Saw them both several times. It's probably safe to say I've seen Tombstone 75 times. I can recite it. I liked Tombstone better personally... mostly because of the cast. Kilmer was great as Holiday, but according to history, Dennis Quaid was closer in appearance - very, very thin from his illness. They said Quaid lost something like 40 pounds for the role and he's not big to begin with.
Both are good. Tombstone is better.