So...is the argument who was a better performer, or who made the better Batman? Because one of them obviously had writing that was more in tune with what most people consider "better Batman", and therefore, even had he given an average performance, would still have been deemed "better" in most regards.
I think, and mostly because I'm a Batman fan and not subject to bias in any way, shape or form, that Christian Bale made the better Bruce/Batman in almost every way, and that he had much better "stuff" to do in his film than Keaton did. I think Michael Keaton did more with his role as an actor than Bale did with what he was given, but every time I say that, I'm not even sure people will get what I mean, which turns into a pissing match, which is in turn, fun.