Okafor has great touch, footwork, and ballhandling for a player his size. He also has shown an ability to pass out of the post when he has teammates to pass to.
Horford is an excellent shooter, screen setter, passer, and floor runner. His main weakness is on the boards, but that would be less pronounced if he were used as more of a hybrid four five than as a full time center.
Okafor has limited range now but is already lethal within ten feet, and has shown the touch and skill level to expand his range out to the three point line. I really think he will ultimately be more like Pau than Big Al on the offensive end.
Horford and Okafor would not be a perfect pairing, but I think they could present a lot of problems for opposing frontcourts. The combined size, strength, and skill level would be off the charts. With a coach like Brad and on court mentors like Horford and Amir, I think Okafor could become every bit as valuable as Pau was at his peak.