Ninja Assassin is over the top action throughout. Battle: LA I think had only one scene where I truly guffawed at the action.
Ninja Assassin was to display ninjas ASSASSINATING! Battle: LA was to display marines going "hoo-rah" and "FRAG OUT" and burninating aliens. Actually there wasn't much burnininating but I just wanted to use that word. They kicked some alien ass after some "lessons learned" after getting their own asses kicked.
For both movies, you don't go to them for a mind-blowing or a "thinking" sort of movie. You go to them to see action because youre a MAN. So, man up. Bitch.