It's been some time since I've used my Wii to emulate, I don't even remember. Checked GxGeo, last update is from 2010. I remember it barely was able to load many games, and that the DS was even able to emulate NeoGeo better. Has anything changed?
I'd say Wii's better, there's a port of FBA with just the neo geo part in RetroArch. Games can only be run from memory so you are limited to 45~MB games. The DS emu runs the games from the flashcart's SD slot and is limited to the DS's lower res.
There's always the VC emu which can run a few of the 50MB+ games but cannot be injected to.
Actual performance is good, compatibility should be the same as the main version because it is a straight port.