First off, don't make decisions based on what other players you (or your opponent) has. Make each positional decision in a vacuum and put out the team that you think is going to score the most points. You start sitting guys cause you are hedging your bets or your opponent has the QB of your WR or whatever, all you are going to do is talk yourself out of playing your best possible line up.
With that said, I am sitting Thompkins in your position. Jennings has a favorable match-up against what has been a pretty terrible Detroit secondary (caveat that defensive stats are notoriously difficult to predict season-to-season) and Pittsburgh has been, and will continue to be a pass happy offense. Common wisdom tells you that is also true of New England, but that hasn't been the case the last couple of years. They are running the ball more and when they do throw, it is to tight ends.
Thompkins might be enamoring, but I am waiting for the new-look New England offense to sort itself out before I risk starting him. I like safe-but-steady plays though, especially this early in the season.