Because you're playing 3v3 singles, I'd recommend mega Metagross. Unlike Lucario, it's much more bulky and better at switching into attacks, and its ability boosts its coverage moves as well as its STAB attacks. Other than that, they're pretty much the same, so use Metagross. By the way, you should probably replace zen headbutt and hammer arm with ice punch and thunder punch for covering the relatively common ground, dragon, and water type walls.
