I've been a Towns guy since the first time I watched clips of both players ---- that hasn't changed though Okafor would be a tremendous consolation prize.
These are the things that stick out to me.....
Okafor --- when the ball is not in his hands he is very soft, lethargic & uninspired. Whether it is defending, picking for his own teammates, rebounding or running the floor he just doesn't seem overly interested in these other aspects of the game. Another major issue with Okafor is IMO he will need to play lighter at the NBA level. This means that it will always be a constant battle of maintaining weight and I'm not sure I trust his ability to keep the weight down and his conditioning up.
Towns --- the major concern is base/core strength and will he have enough of it. I think this will come from simple physical maturity and growing into those size +20 shoes.
Outside of his strength -- the kid has all the intangibles in high doses. There are no question marks around effort, intensity and passion for the game. He's an all around stud that will make teammates better on both ends of the floor.
Again -- both have much to offer but Okafor with his lack of passion without the ball and potential weight/conditioning issues concern me.
Also with Okafor -- you have to worry about fit with Melo and finding someone to cover for him. With Towns - those issues don't exist.