top15 player is too hard, I'd go with top 3 at position.
I think Carter and Pierce are a lot closer than we like to give credit for. Let's play hypothetical ball - if the Garnett trade gets beat out by a PHO trade, and the C's end up running a Perk, Jefferson, Pierce, Ray Allen, Rondo team on the floor for a couple years. Pierce gets fed up and opts out at end of 2010 and tries to jump on to some other winning team (like Carter in ORL this year) - I could easily see people saying the same things around the league about Pierce not being a winner.
That being said - I'd take a melancholy Center over a soft wing any day. (That's what you cannot say about Pierce - teeth knocked out came back, stabbed nearly to death - deosn't miss a game. I'd guess Carter more of a gamer than people realize, and just not as good as a shooter (and relies more on athleticism than Pierce) so he can't/doesn't get by as well when injured.
Interestingly enough a few years back (like 2005 or so) 82 games had Pierce and Carter as two of the best defensive players by their analysis, despite bad defensive reps.
I guess I cut Carter more slack than most, but I'd still prefer the guy who is lazy in the season, but gets it one for the post season versus the guy who just might or might not show up.