I have been to the majority of 3 practices, plus the scrimmage today. It seemed to me today, and the other practices, that Tanner seems more comfortable with his knowledge of the plays and therfore is seeming more athletic in his throwing. But, especially today, he would look to one receiver and wait for him to be open, never check down, or look for another opinion. (Other than one time he found a hole in the line and tucked and ran for a good run).
I think that Sanders is still having all his new knowledge and plays run through his mind as he's in the motion of dropping back and throwing. So it seems like he is slower at the decision and it effects his throw. But he IS looking at all options and using his check down receivers. I think another week, and he will prove to be The Guy.
Pretty awesome though that I think both will rise up, and we will have a good back-up quarterback either way.