For some reason, I think that Myers may have more upside. I think that Philadelphia will have a pretty good season and that Myers has a good shot to be part of it.
At the same time, I had him last year and found it frustratingly difficult to predict whether he'd do well or not. He'd get shelled by the Expos and then blank the Red Sox. He did ok for me but after pulling him off the bench, where I'd missed a good outing, and sticking him in to blow it, I ended up tossing him in to grease a trade or something like that.
Looking at their stats, it's kind of a wash, in which case, I'd go with whoever's team is projected to be better. That'd be Myers. The only other thing is that the last I read, they weren't sure if Philly will be a hitters' or pitchers' park b/c of 'swirling winds'. Whatever that might mean!!