For me it would have been Mario.
Until Saturday that is.
Because if you remember the Liverpool game, Tevez created a superb opening which saw the ball go across the face of the goal and hit the inside of the post. Mario either couldn't be arsed, or didn't take the gamble that Tevez would create something, and a goal chance was missed. On Saturday Tevez did a similar thing and created a chance but this time Dzeko was waiting to poach and finished it off. I also think Dzeko has more hunger. Having said all that, he did miss a couple of relative sitters, albeit he was offside and again being offside is an issue. But all in all, I think Dzeko is the better starter.