The DSTwo's SNES emulation is pretty mediocre.
I mean, CATSFC is miles more accurate than SNEmulDS- but it just runs most games too slowly for them to be really playable without large amounts of frameskipping. SNEmulDS runs on any flashcart, and runs a lot of games at full speed- even if they're filled with glitches. Buying a DSTwo for SNES emulation would leave you a fair bit poorer and extremely disappointed.
The GBA Everdrive point is pretty irrelevant, frankly- it probably won't be fitted to the DS Lite's reduced Slot-2 form factor, it'll be expensive, probably won't integrate with existing flashcart menus, and there isn't any compelling reason to go for an alternative solution over the EZFlash 3-in-1 at the moment- it's pretty much filled the niche perfectly.