Hmm...I think Kmart, not because he's a better player, but because of the system and team he's on. Popovich rests his players during the regular season, keeping their minutes down (even young guys like Leonard). Overall, I think Kmart will be a more impactful player, although he won't get the well rounded rebound, steal, block stats that Leonard will.
Should I drop Marc Gasol? I'm 9th in a 12 team pro league (but have the highest degree of schedule difficulty thus far) and just don't know if I can afford to keep a roster spot held up that long. I would be picking up Trevor Ariza if I did drop Gasol.