Rhys-Meyers is...an explosive actor. But that isn't an entirely laudatory statement. He can bring this electric frisson of energy to a scene, but he can also over-act appallingly. He's interesting, but probably even higher risk than Wes Bentley, who has a comparable appeal. Rhys-Meyers has been my top pick for Harvey Dent for some time.
Armitage's face is perfect for Bruce Wayne. He has that old-school, rugged attractiveness that suits the part so well, and he won't look pug-ugly next to Cavill, like Brolin. Armitage is definitely one of the better picks I have seen here.