I have a galaxy tab 7 inch the first model, and gba works pretty damn good. I play metal slug advanced, pokemon, advanced wars with no noticeable lag. I would say with the untrained inexperienced eye that emulation is 99% even 100%.
For android you should only go with the .emu emulators.
gba.emu never ran into a game that didnt work at great speeds.
gbc.emu supports original gbc pallets for gb and custom pallets.
im just sick of trying to put a 7 inch tab in my pocket. Thats why I came here for a core open source gaming device, with no android, no battery drains, buttons and i can fit it into my pocket with out feeling guilty of accidentally scratching the screen of an expensive device.