I don't like losing either guy, especially since D'Arnaud, if all the hype is correct, is a true blue chip elite start. The type of man that can make a team. Dickey doesn't have a lot of years left. Though if the Jays can get another 4 or 5 out of him, at quality, then it might be okay. He tosses knuckleball, which throws teams off, and knuckleball is a technique, less stress on the arm, as long as they can reach the place. (though it don't matter, batters swing anyway)
Those pitchers do age differently. So 38 or 33 for fastball, probably same difference.