Pretty simple - who's more dominant, and why?

This came up in another thread, and thought I'd move the discussion here rather than threadjack.

In my opinion, Roger Federer is on another planet. Without him in the field, anyone can step up and win a WTP event. Throw him in the mix, and it's a whole other story.

Tiger's a great golfer, no question. However, I believe Federer is more dominant.