I will say upfront that I think Box Plus-Minus is the best method for capturing a players total contribution that's currently publicly available.
http://www.basketball-reference.com/leagues/NBA_2014_leaders.html
Box-Plus Minus - #9
Win Shares/48 min - #11
Value Over Replacement Player - #16
I don't love PER compared to some other ratings because his stats don't take into consideration the "area of effect" on defense or offense. Kyle Korver has a disproportional effect to the offenses he plays on because he is so dangerous it makes other players better.
Kawhi was #36 in PER last year according to Hollinger.