@Neddo
NTSC-J:
Lacks close chase view while racing.
Has a different soundtrack.
NSX GT1 Turbo instead of the LM GT2 (more power, slightly different look, black instead of "gold/brown")
TVR Griffiths have a different Race mod.
Arcade has the manufacturer list in a different order (you unlock the USA/GB manufacturers instead of the Japanese ones)
Arcade also has a slightly different car list.
Also no Corvette Stingray '67 and Mazda Eunos Roadster NB in Arcade
NTSC/PAL
PAL has multiple languages (Spanish, English, French, Italian, German)
Arcade mode is "buffed" (see my video about it where I compare how Arcade mode handles in all the regions)
Arcade Trial Mountain has a jump in the straight at the top most area.
Arcade Gran Valley East has a jump like the others said above.
Arcade Autumn ring has a jump right before going under the bridge at the loop part.
I think GV Speedway has a jump as well the in "S" part between turn 1 and 2. Not sure about this one.
Options menu has the ability to set sound and music volume (NTSC-J only has ON/OFF)
PAL ONLY: Options menu lets you listen to the ingame soundtrack.
In both versions, you can unlock everything by racing in the hard difficulty. However, you'll still have to race C class, B class and A class cars on all tracks to unlock everything.
Hi-Res Tracks are only night tracks and are not recquired to complete the game, nor do you win anything by completing them. They're just time trials.
All three versions have a few glitches here and there. I think NTSC-U version 1.0 has a glitch with the car wash where you would be charged quite a lot of money to wash your car. Or is that in GT2? I forget.
Finishing endurance races doesn't unlock anything. the credits movie only plays after completing the Gran Turismo Championship. However I don't remember if you can watch that movie anytime anywhere or if you have to complete that championship again to view it.
I'm trying to think, but I think that's all the main differences...
BTW, Grand Valley endurance gets you a Black/green or Black/blue Castrol Supra GT
SSR11 endurance 1 gets you the Nissan Silvia S14 LM Edition in either Red or Green
SSR11 2 gets you the Nismo GTR LM Road Car (and it has a race mod)