Admittedly I"m biased but after watching Westbrook for the last 5 games and watching Harden, how does one come to the conclusion that Harden is the better player?
Westbrook was facing a defense that often doubled him to make him get rid of the ball, he was defended by either Wade(a bigger athletic guy) or Chalmers (a terrific defender), and none of them could really guard him. The 4-20 game 5 skews his numbers he was shooting 48% for the first 4 games.
Harden struggled all series to make shots, probably in part because he was guarding LeBron so much he was overwhelmed, but then Westbrook wasn't exactly guarding a non scorer usually guarding Wade. Harden had a dream setup in game 5 when he came in, Wade gets his 2nd foul and you figure OKC is going to attack him with Harden off the dribble the rest of the time, and Harden didn't do a thing. Didn't even try to exploit the foul trouble, there's a reason they took Wade off Westbrook and put him on Harden, they knew he couldn't guard Westbrook with 2 fouls, but probably could guard Harden.
Defensively it's not close, Westbrook is FAR better. Harden shoots it better and is a better playmaker, but then somehow Westbrook still gets more assists and more assists per minute.
I could see them trading Westbrook in a blockbuster deal if there are other issues, maybe he and Durant don't get along, he wants to be the man etc, but from strictly basketball sense to me trading him over Harden would be a HUGE mistake. Westbrook is a year older, a late bloomer who's still learning the game. He often has no clue what he's doing out there and still often is unguardable, harden is a much more polished player.