There's been a lengthy thread about favourite films and multiple threads for each of the Ghibli releases so far, but in the next 2 months all of Studio Ghibli's works will have been released in multiple regions (R1, R2, R2J, R3, R4). My personal collection is fairly split between R1, R2 and R3HK, but seeing as I love all the films so much I don't mind rebuying the films if better versions exist.
The idea is that I'll write below the line what details I know. If you can correct or supply any details (esp NTSC-PAL conversion info and alt angle intro/outros) then post below and I'll update the list:
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Nausicaa
R1: 1.85 anamorphic with English/Japanese audio (2.0) - subtitles and dubtitles. Disc 1 has the film, trailers, some Disney fluff and a Studio Ghibli documentary(dubbed). Disc 2 has the storyboards. The film has branching so if you choose English, you get the English credits and if you choose Japanese, you get the Japanese ones.
R2J: 1.85 anamorphic with Japanese (2.0) audio and English subs and commentary track - unsubbed. Studio Ghibli feature and storyboards on disc 2.
R3K: direct equivalent of the Japanese version with Korean dub and subs.
R3HK: More muted colours than R2J/R3K. Thanks to Shingster for the R3 details.
R2/R4: 1.85 anamorphic with Japanese / english (2.0) audio - subtitles and dubtitles. NTSC-PAL conversion. Studio Ghibli documentary (subbed). Storyboards on angle 2 - no alt intro as with R1. Trailers.
DVDBeaver link R1 appears most compressed. R2 offers the documentary undubbed, but has an NTSC-PAL conversion transfer.
Laputa: castle in the sky
R1: 1.85 anamorphic with English (Disney dub) (5.1)/Japanese (2.0)/French (2.0) - subtitles and dubtitles. Disc 1 contains the usual Disney fluff (John Lassiter intro and "behind the mike"), trailers and film with alt. intro/outro. Disc 2 contains the storyboards. Title drops the word Laputa.
R2J: 1.85 anamorphic with English (Streamline dub) (2.0)/Japanese (2.0) - English subtitles. Disc 2 has trailers, storyboards and a textless intro/outro. LE contains 2 OST discs.
R2 (Buena Vista): Now deleted; 1.85 anamorphic with English (Disney dub) (5.1)/Japanese (2.0)/French (2.0) - dubtitles only, 8mins of storyboard, and trailers. Title drops the word Laputa.
R2 (Optimum): Same as R4 version.
R3HK: 1.85 anamorphic with Japanese (2.0)/Cantonese (5.1/DTS) - English subtitles. Disc 2 has storyboards and trailers.
R4: 1.85 anamorphic with English (Disney dub) (2.0)/Japanese (2.0) - English subtitles and dubtitles. NTSC-PAL conversion. Textless intro/outro, storyboards, trailers. nb - bad layer change.
New English dub has rescored music by Joe Hisaishi.
DVDBeaver link
My neighbour Totoro
R1 (Fox): Pan/Scan, English only.
R1 (Buena Vista): Anamorphic (windowboxed) with Japanese (2.0)/English(2.0) dubs - English subtitles and dubtitles. Disc 1 has Behind the microphone feature, textless intro/outro and trailers. Disc 2 has complete storyboards.
R2J: 1.85 anamorphic with Japanese(2.0)/English (old dub) (2.0) - Englsih dubtitles. Disc 2 has storyboards, 2xfeatures (making of and Ghibli museum), textless intro/outro and trailers.
R2: Anamorphic (windowboxed) with Japanese (2.0)/English(2.0) dubs - English subtitles and dubtitles. film-to-PAL conversion

Has storyboards, textless intros/outros and trailers.
R3HK: 1.85 anamorphic with Japanese (2.0)/Cantonese (2.0) - English subtitles. Disc 2 has storyboards and trailers. Initial release was on DVD5, but subsequent pressings were on DVD9 even though the case says DVD5.
R4: As R2.
Grave of the fireflies
R1CE: 1.78 anamorphic with English (2.0)/Japanese (2.0) - English subtitles. Disc 1 has storyboards as an alternate angle. Disc 2 has 3 DVNR doc, Then and now doc, interview with Roger Ebert, Historical Perspective, interview with Isao Takahata, deleted scenes, promo and trailers.
R2J: 1.78 anamorphic with English (2.0)/Japanese (2.0) - bad English subtitles. Making of and trailer
R2: same specs as R1CE - picture a bit softer. NTSC-PAL conversion.
R4: sames as R2
DVDBeaver link
Kiki's delivery service
R1: anamorphic 1.85 with English (5.1)/Japanese(5.1) - English subtitles and dubtitles. Disc 1 has the Disney fluff and trailers. Alternate angle intro/outro (English version has bad PQ). Disc 2 has storyboards). Slight sync problem with effects track.
R2J: 1.85 anamorphic with English (2.0)/Japanese (2.0) dub - English dubtitles (from Streamline dub). Disc 2 has storyboards, trailers and Ursula's Painting feature.
R2 (Buena Vista): Now deleted 1.85 anamorphic with English (5.1)/Japanese(5.1) - with English dubtitles (HOH). Storyboards in 4:3.
R2 (Optimum): Same as R4.
R3HK: 1.85 anamorphic with Japanese (2.0)/Cantonese (5.1) - with English subtitles (from Streamline dub). Disc 2 has storyboards, Ursula's Painting and trailers. Initial release was on DVD5, but subsequent pressings were on DVD9 even though the case says DVD5.
R4: 1.85 Anamorphic with English (2.0)/Japanese (2.0) dubs - English subtitles and dubtitles. Storyboards, Ursula's Painting and trailers
DVDBeaver link
Only yesterday
R1: Not released
R2J: 1.85 Anamorphic with Japanese (2.0) dub with English subtitles. 2nd Disc has 46 min documentary (in Japanese with no English subs), storyboards and trailers.
R2: 1.85 Anamorphic (film-PAL) with Japanese (2.0) dubs - English subtitles and dubtitles. Storyboards, and making of.
R3: not certain - extras listed as storyboards, intro to Studio Ghibli (unsubbed) and trailers
R4: same as R2
Porco Rosso
R1: 1.85 anamorphic with English (2.0)/Japanese (2.0)/French (2.0) dubs - with English subtitles and dubtitles. Disc 1 has Disney fluff and an interview. Disc 2 has the storyboards. The French dub is Miyazaki's favourite.
R2J: 1.85 anamorphic with English (old dub) (2.0)/Japanese (2.0)/French (2.0) dubs - with English subtitles. Storyboards, interview (unsubbed) and trailers.
R2: 1.85 anamophic with English (2.0)/Japanese (2.0) dubs - English subtltles and dubtitles. Storyboards, trailers and interview.
R3HK: 1.85 anamorphic (despite what Rewind thinks) with Japanese (2.0)/Cantonese (5.1/DTS) dubs - with English subtitles. Disc 2 has storyboards and trailers
R4: same as R2
Ocean Waves
R1 Not released
R2 Not released
R2J 1.85:1 anamorphic with Japanese (2.0) dub - English and Japanese subtitles, 50min Documentary. Disc 2 has storyboards and trailers
R3HK Unknown
R4 Not released
Pom Poko
R1: 1.85 anamorphic with English (2.0)/Japanese (2.0) dubs - English subtitles and dubtitles. Disc 2 has trailers and storyboards.
R2J: 1.85 anamorphic with Japanese (2.0) dub - English subtitles. Disc 2 has storyboards, tanooki feature (unsubbed) and trailers.
R2: 1.85 anamorphic with English(2.0)/Japanese (2.0) dubs - English subtitles and dubtitles. NTSC-PAL conversion. Storyboards and trailers.
R3HK: 1.85 anamorphic with Japanese (2.0)/Cantonese (5.1/DTS) dubs - English subtitles. Disc 2 has Storyboards and trailers.
R4: same as R2
Whisper of the heart
R1: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - English subtitles and dubtitles. Behind the microphone feature. Disc 2 has trailers and storyboards.
R2J: 1.85 anamorphic with Japanese (5.1/2.0) dub - English subtitles(?). Trailers and storyboards.
R2: 1.85 anamorphic (film-PAL) with English (5.1)/Japanese (5.1) dubs - English subtitles and dubtitles. Trailers, storyboards and a feature about the Iblard artwork.
R3HK: 1.85 (anamorphic?) with Japanese (2.0)/Cantonese (5.1) dubs - with English subtitles. Disc 2 features storyboards and trailers
R4: same as R2
Princess Mononoke
R1: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles. Trailer and English dub feature. Alt angle intro/outro.
R2J: Disc 1 has 1.85 anamorphic with Japanese (5.1/2.0)/English (5.1) dubs with English subtitles. Disc 2 has storyboards. Disc 3 is 1.85 anamorphic with internation dubs (2.0) and trailers.
R2 (Buena Vista): Deleted. 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English dubtitles. Same features as R1. Alt angle intro/outro.
R2 (Optimum): Not released (scheduled for 27/03) - probably the same as R4.
R3HK: unknown
R4: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. NTSC-PAL conversion. Storyboards and trailers.
DVDBeaver link
My neighbours the Yamadas
R1: 1.85 anamorphic with English (5.1)/Japanese (5.1) with English subtitles and dubtitles. Behind the microphone feature, trailers and static storyboards
R2J: 1.85 anamorphic with Japanese (5.1/2.0/DTS) dubs - English and French subtitles. Disc 2 has a feature containing one scene of animated storyboards and trailers and a menu-driven storyboard/Manga comparrison. 20 page booklet.
R2: 1.85 anamorphic (NTSC-PAL) with English (5.1)/Japanese (5.1) with English subtitles and dubtitles. Trailers and static storyboards
R3: not certain - probably storyboards and trailers
R4: same as R2
Spirited Away
R1: 2.00 anamorphic (1.85 windowboxed) with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. Much less red-tint. Disney fluff, art of Spirited Away. Disc 2 has storyboards (10mins), trailers and Nippon TV special (subbed). Alt angle intro/outro
R2J: 1.85 anamorphic with Japanese (2.0/DTSES) dub - with English subtitles. Disc 2 has storyboards and trailers. Has red tint.
R2: 2.00 anamorphic (1.85 windowboxed) with English (5.1)/Japanese (5.1) - with English subtitles. NTSC-PAL conversion. Disc 1 has storyboards. Disc 2 as R1.
R3HK: 1.85 anamorphic with Japanese (2.0/DTSES)/Cantonese (2.0) - with English subtitles. Disc 2 has storyboards and making of (not subbed). Has red tint.
R4: 2.00 anamorphic (1.85 windowboxed) with English (5.1)/Japanese (5.1/DTS) - with English subtitles and dubtitles. NTSC-PAL conversion. Disc 2 has 5 storyboards, notes, Nippon TV special, trailers 3xfeatures
R2/4 have bad PQ.
DVDBeaver link
The Cat Returns
R1: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. Behind the microphone, Making of, trailers. Disc 2 has storyboards.
R2J: Anamorphic 1.85 with Japanese (2.0/5.1/DTS) - with English subtitles. Ghiblies episode 2. Disc 2 has storyboards, making of, NTV special and trailers.
R2: 1.78 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. NTSC-PAL conversion. Storyboards, making of and trailers.
R3: unknown
R4: Same as R2 except 1.85 anamorphic.
DVDBeaver link
Howl's moving castle
R1: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. Behind the microphone, Interview with Pete Docter, Miyazaki @ Pixar, trailers. Disc 2 has storyboards.
R2J: Anamorphic 1.78 (window boxed) with Japanese (5.1)/English (5.1) dubs - with English subtitles(?). Disc 2 has storyboards, Venice feature, Wynne Jones interview, Pete Docter interviewand trailers. SE has extra version of filmJapanese DTS but no subs and another disc with Moebius and Miyazaki feature, US Premiere , Miyazaki @ Pixar and a CG feature. Features have no English subs.
R2: 1.85 anamorphic with English (5.1)/Japanese (5.1) dubs - with English subtitles and dubtitles. Disc 1 has storyboards and Ghibli trailers. Disc 2 has interviews with Pete Docter and Wynne Jones, Miyazaki @ Pixar, CG feature and trailers.
R3HK: 1.85 anamorphic with Japanese (5.1EX)/Cantonese (5.1) - with English subtitles. Disc 2 has storyboards, interviews with Pete Docter and Wynne Jones, Miyazaki @ Pixar, CG Feature and trailers.
R3K: 1.85 anamorphic with Japanese (2.0/5.1/DTS)/Korean (5.1) - with English subtitles. Disc 2 has storyboards, interviews with Pete Docter and Wynne Jones, trailers, biographies and Korean dub feature. Disc 3 has Miyazaki @ Pixar, CG feature and more trailers.
R4: Unsure - seems to be same as R2.
Whiggles picture comparisson
So there we have it. Best versions to get wil change depending on your posts and as new specs come to light.
Nausicaa of the valley of the wind - R1/2/4 decent (subbed) extras and good PQ
Laputa: castle in the sky - R1/R4 new dub/music and good subs
My neighbour Totoro - wait and see; R1/4 may be better than Aisian versions. R2 looks pretty decent from the DVDTimes review.
Grave of the fireflies - R1 R2/4 have slightly soft picture
Kiki's delivery service - ? R1 has unsynced effects, R2J has dubtitles
Only yesterday - R2/4 R1 not available for forseeable future
Porco Rosso - R1/R2J have Miyazaki's prefered French track. Depends on whether you want the Streamline dub or the new Disney dub.
Pom Poko - R1/R2/R4 English dubs and despite NTSC-PAL, R2/4 have decent PQ
Whisper of the heart - R1/R2/R4 - depends on whether you want higher PAL resolution or correct pitch sound
Princess Mononoke - R1/R2J/R3HK R1 has a quite different look to the other 2. Compare them at the DVDBeaver site and decide which you prefer.
My neighbours the Yamadas - R1/R2/R4 - depends on whether you want higher PAL resolution or correct pitch sound
Spirited away - R1 no red tint and better PQ than R2/4 even though R4 has DTS
The cat returns - R1/2/4 see Pom Poko
Howl's moving castle - From the comparisson, the R2 is the best. R2J is too soft and R1 has compression issues.