@PogueSquadron I'm not totally confident in my position on FX Chip emulation, but one thing I DO know is that Nintendo isn't Machiavellian enough to hold all FX games for the WiiU. Hell, they're not even organized enough!
I'm grateful to have the GBA version on my 3DS (because Yoshi's Island in any form is awesome, and especially in handheld form), but it's still not as good as the SNES version.
Eh... I dunno. I mean yeah, the "Touch Fuzzy, Get Dizzy" stage runs smoother on the SNES, and I suppose the "morphing" animation is technically better too, but those are just small complaints on an overall amazing game. The GBA version does come with even more stages, which I think is pretty cool, and having it on a portable to play whenever I want is fantastic. Plus it also comes with that multiplayer Mario Bros. game that is more addictive than it really should be.
I know this is kind of "typical" of me to choose the portable version of a game over the console version, but I honestly do believe the GBA version is a better package. Though having this gem on the Wii as well would certainly be welcome.
The additional stages are definitely something the GBA version has over the SNES version, although to be honest I'm not sure I even unlocked all of them. The visuals are better on the SNES though as you mentioned, and I think the music sounds better on the SNES than the GBA. But having it portable is a HUGE advantage. If the SNES version were on the 3DS, it would be no contest.
Oh yeah, there's Mario Bros. too I guess, but I never put much time into that (on any of the 500 games it was included with).
I think just because the grids are smaller doesn't make the game amy less difficult, there are some real head scratchers here, its a shame the game doesn't support DLC or create your own puzzles, I agree with the current consensus that Pushmo style QR codes would be amazing. There is some difference in colour coding.of the numbers during varying stages of column/row completion too although I can't remember what they are off hand.