Bulger has been basically worthless for me, where Pennington seems to be about as good (or mediocre) as anyone expected of him.
Bulger is Vs Dallas- Not a great pass rush, but aggressive corners (who could get beaten)
Pennington is Vs Buffalo- Supposed to be a decent defense but has not lived up to it yet.
Neither matchup makes it a clear choice. However, Steven Jackson (who I also have ) is hurt, so Bulger will have to put it in the air if they are going to win.
By the way, did I mention that Bulger and Jackson are killing me?