What they all said, the o3ds reboots granting more RAM for games at the cost of almost no multitasking. (Browser, miiverse and other functions get disabled as well in these titles)
So far o3ds has Smash, MH4U/MHG, PokemonS/M, SMM3DS, among a few others more. It's tricky to get something like NTR working on those games, even if rewritten from scratch. because when the o3ds reboots it kills any suspended processes.