I'm going with Myers. He's still young, stepped up considerably and there is still a lot of room for improvement.
Cain did not have a good season in the minors in 05. He did pitch extremely well in his brief stint in the majors but I'm not totally sold yet. I think he will hit more than his share of bumps on the road.
"Think of how stupid the average person is, and realize half of them are stupider than that." ~George Carlin