Which Version Should I Get?
NTSC-J (1.0) is the best version to get if you want to play on the fastest version for ALL categories. After that come the J1.1 and J1.2 versions. Then U1.0>U1.1.
You don't want to play on the PAL version. Even though Yoshi runs (in game) at a higher speed, the game itself runs at 50Hz which makes it slower overall, unless you play on a 60Hz modded console, which would invalidate your run anyway, so don't run on PAL, pal ;)
So What Is Different Anyway?
⦁ The Japanese version of the game has fewer text boxes, which means that a little bit of time will be saved. If you are planning on playing Any% (ACE/Credits Warp), J1.0 is the only version the whole category works on. It's also the fastest version for the Null Egg categories.
⦁ Text boxes work different between J and U. On the J version, text boxes work like "pages" whereas with the U version of the game, they are more "fluid".
⦁ In J1.0 & U1.0, there is a glitch that you can do in 6-5 where you tongue a ghost shy guy before it comes out of the pipe and if you spit it out afterwards, it will start flying in a straight line, unlike in 1.1/1.2, where it will take the normal flying arc.
⦁ In 6-7, in the room before the final room, there is an additional bandit and potted jumping cactus enemy.
⦁ In 6-E, there is a room that spells out "YOSSY" with platform guides in the J Version and "YOSHI" in the U Version.
⦁ Other changes include a slightly different pause menu and score screen. On J1.0 it says, "STAR", "COIN", "FLOWER" and "TOTAL POINT", whereas in J1.1/1.2, they added the "S" to each of the words. The U version has this fix as well and on 1.1 a bolder font.
You can see an extensive list of differences with images here: https://tcrf.net/Super_Mario_World_2:_Yoshi%27s_Island/Version_Differences
But How Do I Know Which Version I Have?
You can tell very easily whether or not you have U/J/PAL but to find out the exact version, you want to look at the back of your cartridge and search for a little imprint (refer to the picture, which has a "40A" imprint which means it is version 1.1). The number appears to be random, so that isn't important.
- Number only = 1.0
- Number + A = 1.1
- Number + B = 1.2
You can also just look at the pause menu to determine what version you have.