Wiggins has won the Tour, but he can't win a race that lacks a TT. Also after the Olympics he hasn't shown any kind of form or motivation.
Boonen and Purito have had solo and sprint wins in many kinds of races, but Purito has the upper hand imho. He's podiumed two GT's, plus 5(!) stage wins, and he's just added a monument to his palmares. Boonen hasn't won any important race since Roubaix.
So Purito has to take this, especially since he's my favourite rider