uh...depending on which Batman version you're talkin about.
West was superb as the campy Batman that reflected the comics in the 60s.
Keaton looked like the hardcore Batman that comics decided to return to after the campy 60s. He may not look like much of a Bruce Wayne..but in costume, I think he pulled off the menacing Batman quite nicely.
I have to agree with Spy. It really depends which kind of portrayal you go for. West and Keaton are so different in style and in when they did the role, so it is not a fair question to judge one based on the other. Now, if you had asked who was better- Keaton or Val Kilmer, then that would be more fair in my opinion.