Sell high if you can, definitely, because despite the numbers he's capable of putting up he could become the next Jesse Foppert or Edwin Jackson. I remember those guys were hot commodities for awhile... el sucko. Granted, Prior was great for a little while and there's always the possibility he'll hit the ground running.
What I'm trying to say is, if you can fill a bigger hole somewhere else with a proven commodity then it's hard not to hesitate to move Hamels. Hype is powerful.