I'll say this, Bale definitely benefits for more fleshed out material, and that he's younger and more comparable to Batman when it comes to physicality, but the more I watch Begins, the more annoyed I am everytime he's on screen as Batman. The things Keaton did effortlessly with his eyes and his voice, Bale just can't seem to pull off. The whole guttural animal voice Bale does for Batman just comes off very forced to me. And the more I think about the public Wayne persona, I think they may have gone a bit overboard with the smarmyness. Him pretending to be drunk at his birthday party, I suppose that was necessary, but couple that with the dinner with the two models, swimming with them in the fountain, and pulling out his checkbook saying he's gonna buy the hotel, it's all a little much. Wayne has to be a different person compared to Batman, but he doesn't need to be a complete and total prick.
I think Keaton as Wayne sells so well, because it's not just how he acts as Wayne in public, it's how people react to him. It always goes back to Knox and Vicki in his trophy room, for me. The make the usual assumptions about him because he's rich, and cracking jokes about the man, then he shows up behind them and pretty much puts Knox in his place without even trying to. It's like he doesn't even realize what he's doing. Keaton's whole delivery of "Because I bought it in Japan." is just classic, 'cause there doesn't seem to be even a hint of "duh, isn't it obvious" snarkiness to it. He just says it in such a matter-of-fact way, where for the most part, he's merely answering Knox's question, but at the same time he's making him feel like a doofus for not knowing where the armor was from. And then, even after he's chatted them all up and come off like a nice guy, Knox still has his doubts about him, tying it all into him just being some shallow rich guy. Then it's followed by this great cinematic reveal as they pull back the shot with Knox and Vicki looking at the mirror, then we see the cameras behind the mirror, then the monitors in the batcave, then Bruce, and just about everything about his demeanor has changed. All the charm and wit he exhibited earlier is gone from his face, and you just see this stern, determined look on his face, and you know that's who he really is.