SAR is the better player, but that's not really what's important. Starting SAR recreates the same problem we had last year. Especially if Kevin is supposed to have some sort of breakout year offensively. Ron may not average quite as many points as Peja, but he actually needs more shots to get his, and wants/needs to handle the ball a lot. Kevin is primarily a scorer, and stepping into a role vacated by a guy who had a tremendous year doing the other things as the closest thing to a roleplayer our original starting lineup had. And so you are again talking about a tremendous shot crunch if SAR is the starter. Also absolutely no rebounding -- not even a Bonzi to try to cover it up.
SAR did his best work off the bench last year -- the relatively one dimensional score, score and score some more season he had was well suited to a 6th man role. Meanwhile Kenny pretty much refused to play off the bench and gave a much better effort, not to mention, roleplayer, in the starting lineup. Without thinking Kenny is anything more than a garbage starter, there is still a good argument to be made for why he should do so anyway. Might strengthen the starters AND strengthen the bench (who otherwise would be lacking a proven scorer).