My take:
Lakers win that trade--Nash and Howard are borderline useless, and the notion that Westbrook is a ballhog (with the implication being he should do nothing but feed the ball to Durant on most plays) is at best misguided, and at worst painfully incorrect.
If you take Westbrook off that Thunder team, who else is going to score and initiate the offense? Steve "I actually fell apart in 2008 but the PHX medical staff kept me all duct taped together" Nash? Dwight "never going to be the same" Howard?
For better or worse, Westbrook has actually been a better basketball player than Nash over his first four seasons--and when you factor in the fact that Westbrook has a much higher ceiling and is significantly less injury prone... it's no contest. LA does that in a heartbeat, even if it means having to deal with Perkins.
And here are the Nash/Westbrook numbers, for the doubters:
http://bkref.com/tiny/6SFV5