I'd take Portis 10 times outta 10 over Looney. Looney is ages away from being a capable four. If anything, I think Looney's future is as a wing player with the capability of playing a face-up four in spot minutes. Kaminsky or Lyles is our guy.
Given that Portis is a full year older than Looney, it is hard to say that Looney wouldn't have had a better season next year. I just see Looney as a player that fits with the more wide open NBA better. He has better length and outside shooting ability.