If the Celtics have to choose between Jared Sullinger and Kelly Olynyk, who should they keep?

The Celtics could potentially have a power forward dilemma at some point this offseason.  They are looking to upgrade the talent on the roster and they will not be constrained by position.  If the best free agent, trade, or draft prospect they can get is yet another power forward, that's who they'll get.  Even if they don't go out and add a power forward, they still have the luxury of re-signing Brandon Bass.

All of which points to having too many power forwards.

Sure, you can play them together in a quasi-positionless lineup where someone matches up with the other team's 5.  There aren't a lot of centers out there that can make the team really pay for that kind of mismatch anyway.  Stevens managed the rotations pretty well this year despite the glut at the position.  Still, it isn't ideal.

At some point the team might have to focus on developing either Kelly Olynyk or Jared Sullinger and providing them with a clear backup (either a young player or veteran role player like Bass).  That would also allow them to move one or the other of them to fill needs elsewhere on the roster.

Which begs the question in the title of this post: Who would you rather keep?

Jared Sullinger is seemingly farther along in his development at this point. He's got a crafty back-to-the-basket game, rebounding chops, and is developing a 3 point shot to stretch the floor (or at least keep defenses honest).  The problem is that he's struggled with conditioning and has to prove that he can stay in shape (and on the court) enough to help on switches late in the game.

Kelly Olynyk is a modern, face-up, stretch 4 with a lot of talents.  At his best he's hitting shots from deep, driving into the lane for easy buckets, and displaying deft passing instincts.  At his worst he's a deer in headlights afraid to shoot the ball and ineffective on either end of the floor.  He has less experience than Sullinger, so this year should tell us a lot.

So who would you pick?  If you could trade one of them to upgrade the roster (either by trading up or by adding a piece elsewhere), who would you want to keep?  Obviously the answer will always be "it depends on a lot of things."  But take the variables (like "who would another team rather have?" or "who brings back the most in return?") out of the equation.  If a team is willing to deal with you and take either one in return, who do you want here next year?

I'm tempted to say Sullinger just because he's proven that he can be one of the best players on the court and I'm a sucker for rebounders.  On the other hand, he hasn't proven that he can master his own body.  Also, the following blurb from Grantland's Zach Lowe gives me pause.

We Interrupt This Eulogy for the NBA Post-Up Game to Bring You Its Rebirth "

"If you’re a stretch 4 today, you’d better have a lightning-quick release," says Daryl Morey, the Rockets GM. Guys like Ryan Anderson, Ersan Ilyasova, and Channing Frye are more multidimensional, but they aren’t as lethal as they were two or three years ago, and they can only thrive in specific environments. If they had better post games, they could beat up smaller defenders and force opponents into uncomfortable readjustments. But they can’t — at least not consistently. A few executives have dumped the term "stretch 4" altogether and replaced it with "playmaking 4" — a term I’m officially stealing right now. Shooting is nice, but it’s not enough anymore as defenses get smarter, faster, and more flexible working within the loosened rules. Spot-up guys have to be able to catch the ball, pump-fake a defender rushing out at them, drive into the lane, and make some sort of play. If they can’t manage that, a possession dies with them.

Olynyk seems to fit the description of a guy that can get past his defender and make a play in the lane.  I can see why Danny Ainge and Brad Stevens both had (and have) high hopes for this kid.  Enough that they moved up in the draft to get him.  He fits the mold of modern NBA big man except that he doesn't play great defense, and that might ultimately doom him.

So I'll throw this open to the comments and this poll.  Who ya got?