Eh, disagree, the sound difference bothers me there a lot more than it does in Yoshi's Island. That and the GBA Yoshi's Island actually has more levels to it. SMA2 is nice for the fact that it fixed Luigi's sprite and offered him as an alternate in single-player, but it did so at the expense of 2-player (which SMA4 preserved somewhat), and it made no other significant changes other than throwing colored Yoshis into regular stages (pointless since this is before Nintendo forgot how to let you keep Yoshi between levels).
Really? I always thought the sound was so basic in SMW that the sound quality decrease from the GBA's awful soundchip wasn't a big deal at all. In Yoshi's Island songs like the final boss battle don't sound as cool. And I also dislike how the colors are all lightened up. Also I [tornado fang]ing hate that goddamn Yoshi's Story voice they jammed in (Though the addition of voices is something I didn't like in ANY of the Mario Advance Titles, if mostly because they sounded terrible.)
SMW had that issue too but since I don't bother with 2-player anyway it was nice to have Luigi playable as a not-palette swap of Mario.
That, and getting hit didn't force you down to Small Mario like it does in SNES World.
GBA Yoshi's Island's extra stages aren't really good anyway.
Who knows, maybe they'll be smart and make the games sound better, but knowing their insistence on being exactly like the original I doubt it.