I'm bumping this thread because I'm facing the same choice.
On the one hand, Vick showed up against the Jets, who have an elite defense, and he ran the numbers on them. Dallas isn't as good, and he tore them apart earlier this year. Then again, he could just have one of his trademark bad days and ruin your (our) day.
Tebow seems like hes trending up, improving with each game. Unless hes devastated by the loss to New England (which, given his sunny exposition I highly doubt) hes more likely to do even better against an inferior team.
Tough call. I'm going to sleep on it and get back to you.
10 Team, .5PPR, Keeper
QB: Stafford, Taylor
WR: Julio, Nelson, Cooper, Marvin, Shepard
RB: Bell, DeMarco, Gurley, Bernard, D Williams, Morris
DST: Kansas City, New England