I'm not sure I'd even touch Bynum unless I had Phoenix's trainers. It's one thing to be injury prone, but he's also never taken his rehab all that seriously. I gave Bynum the benefit of the doubt not long ago because he's such a rare talent, but the flamenco dancing in Spain a month after having his knee scope would be the last straw if I were a GM.
Dog-piling Howard has become everyone's favorite hobby because he's an unlikeable person, but the guy put up 17 and 12 with a bad back on a highly dysfunctional team. His defense wasn't up to his standard, but he rushed his return from back surgery, and his team was a dumpster fire orchestrated by a coach that couldn't care less about defense. If you give him a full summer to heal, get him a good coach (like the one he got fired in Orlando), and make him a primary offensive option (a clear-cut #1 or #2), I think Dwight will look a lot like his old self.
Howard is two years older than Bynum, but I'd be shocked if Bynum isn't out of the league first. Bynum's age means very little with those knees.