Okafor would help their offense, give them better floor balance and I think being on a veteran team would help him a lot defensively.
i) You cant just use paint DFG%, especially for players who're on a dysfunctional team with lineup changes all throughout the season.I'll also add that Noel's paint defensive field goal percentage allowed isn't much better than Okafor's.
Edit: actually, it's worse.
ii) Noel started in nearly every game he played in, therefore he defended against the best offensive players (avg 29 min a game), whereas Okafor came off the bench for most of the season (avg 20 min a game)
iii)