OR/AS, it accepts all new moves, mega evolutions and is a nice place to get about (lets not forget not needing fly on a pokemon!)
X/Y just seems a bit meh after I completed the game and I prefer to breed etc in OR.
With Pokemon bank its easy as anything to transfer all your mons, I have powersaves also so have backud up my complete pokedex to the bank and keep it on my cartridge too as well as copies of all my main team.