Who should I keep in fantasy football?

My friends and I are in a league and each year we are allowed to keep 2 people. I am most likely keeping Addai and the other slot is open for either Romo, marion barber, or larry johnson. Rb's are usually more valued in our league than other positions. I have been seeing Larry higher in mock drafts previously, but marion barber has been making top 7 or 8 on other mock drafts. Larry Johnson's weak pre season has also been making me confused