The Super Card SD is about $30 cheaper, and it says it also has gba support, whats the differences between the two.
super card claims to have GBA supoort, but, it barely does. It will play GBA games, but they will play poorly. supercard also isn't as power efficient so the battery will last not as long as with M3. M3 is worth the $30 extra.
if you want true GBA support, also keep in mind the M3 Pro series does NOT have this. It has very little support for GBA. So if you want to get one that plays GBA, get the original M3 (not pro version)
