I'm indifferent towards Howard. 6'10 centers who can barely play with their backs to the basket and have shown very little improvement in their skill set since their rookie year tend to put me off a bit. Dude is a freakish athlete for sure, and durability is certainly a factor in the decision, but beyond athleticism and durability, where does Howard outshine Bynum?
More importantly, is athleticism and durability enough? Bynum is a more talented basketball player. He's bigger and longer. He's not the shot blocker Howard is, but he controls the paint better. Bynum has softer hands, more range, and can hit free throws. Bynum is a better passer.
One final thing - swap Bynum for Howard and keep the rest of the teams the same. Now, Howard goes from being the #1 option with 30 touches a game to the #2 option with 15. Bynum goes from 15 touches to 30. What sort of numbers will they put up?
I'd say: Howard averages 16 and 13, Bynum averages 25 and 15.
In other words, all else being equal, Bynum and Howard are, too.
So maybe durability IS enough?