you arent considering the option that he could actually make the shot... if it goes in, that is better than (a miss and) an offensive rebound, and is worth 150% of the two point shot that would result from the o-reb. he doesnt need to grab o-rebs when he makes the shot... 3 pt shots and ft's are the most efficient shots in basketball. a 35% 3-pt shooter is equivalent to a 52.5% 2-pt shooter. if you have someone who can make them at a decent clip, (who knows if kanter is that guy or not -- just speculating --), then i think you have them take that shot, no question.
That's too simplistic, because as you know, whereas a missed 3's is a free-for-all, but a missed 2 close to the rim means the shooter has a pretty decent chance of grabbing his/her own rebound and put it back in.
Speaking of this, I believe Kanter is probably the best player on our team in grabbing a rebound off of his own missed shot and putting it back in.