Yet another "which lens thread"

I am trying to decide between these lenses at the moment, so any advice gratefully received. I intend to use it for action shots, shooting footy/soccer and surf lifesaving, using a 1D Mk II.

With the dollar at the moment, the Canon is almost the same price as the Bigma usually is, so it's pretty attractive.

My main criteria are image quality and AF speed. Surf lifesaving in particular often has objects (people, boats, waves) moving towards the shooter at a great rate of knots, so AF speed is critical.

In terms of image quality, I hear mixed things about the Bigma, which seems to be the main criticism.

The main downsides I hear about the Canon are the push-pull zoom and the description "dust pump".

The extra 150mm reach on the bigma would be nice, but is less of an issue than the other two factors.

So, advice, war-stories etc appreciated, especially from those that have switched between these particular lenses (if so, why did you change ?). Almost all my other lenses are Canon L's, so would I regret jumping ship ?

Thanks