Depends on what the rest of your team looks like and your lineup rules.
Just on it's own, I would stick with Stafford/Johnson. I'm pretty high on Stafford this year, but there is the injury risk with him. No, I don't expect him to do as well as Brees. But, I expect the difference between Stafford and Brees to be less than the different between Johnson and Thomas. So you are giving up more in WR points than what your are gaining in QB points.
10 team, PPR, 1 qb 1rb, 2wr, 2flex (rb/wr/te), 1k, 1dst
QB: Stafford, E. Manning
RB: Peterson, Blount, Hightower, Starks, Tate, Tolbert
WR: Nicks, Wayne, Bowe, S. Johnson, M. Thomas