My gut feeling is that Thomas Tapeh is a very underrated player and the only thing he lacks is experience. The Ritchie loss will hurt Westbrook a little. Take a look at Westbrook's rushing numbers from the Lion game after Ritchie went out. (Of course they had NO fullback dressed as they deactivated Tapeh - numbers reason only - before the game.)
Parry had a very solid pre-season and is an effective blocker and can catch a pass too.
Tapeh is not as good a blocker (he hasn't seen the different blitz schemes and might miss an assignment here and there), but can run the ball well too.
In conclusion, I'd move BWB from a weak #1 FF RB to a very strong #2 FF RB.