No native hacks worth mentioning, more annoying to hack for old games, less than optimal for GBA games, less than optimal for some types of homebrew, lower battery life (it is a portable console after all), more expensive and arguably nogamesgaems at present ( http://gbatemp.net/threads/android-as-a-viable-alternative-to-the-3ds-and-maybe-vita.345121/ ) and depending upon your tastes not a terribly rosy future either.
Bad might be a stretch but 3ds outright better at present is "time to take up yoga if you enjoy stretching that much".
Really? Where you have been?
Hacks? why you want hacks?
You want GBA Games? buy a DSTwo and the GBA games will be coming to the VC sooner or later
Srsly Android Shitty games for the 3DS and PS Vita? Who want to play those "games"