Okafor.
Kid is 19 years old isn't he? So he's hella young and can still be shaped by Coach Brad into a franchise big man.
A lot more risk involved with Bender. Could be an epic bust but could be what Colangelo always wanted Bargani to be in Toronto.
Okafor will never be a franchise big man, no matter which team or coach he plays for. He doesn't have the talent to be that good. He never even projected to have the talent to be that good.
He could potentially become an all-star in the right situation (fit is VERY important for Okafor due to his limited skill set) but when you say franchise player you're talking about guys like Anthony Davis, Demarcus Cousins, Leborn James, Kevin Durant, Tim Duncan, Kevin Garnett, etc. Okafor will never come remotely close to being as good as those guys.
Towns on the other hand...he has that potential. As does Simmons. Maybe Ingram.