Well, the first topic of discussion would have to be the system that will be in place. IF it is a one back system, as this article claims
Scout.com: Scouting the 'Skins Running Backs, it will definitely be portis. Betts, as of now, has no shot to take the spot from portis and in that system portis will have far more yards. If we are going to play running back by committee then i hope it will be too close to call. I hope that both of them end up with similar carries and yards so that if either had more it wouldn't be statistically significant. Yesterday i was reading an article saying that they probably will be on the field together, much of the time. Betts' yardage really has to do with what saunders does.
How did Saunders balance LJ and Priest back in KC? I mean, when priest went down LJ picked up the slack(big time). But what where LJ's numbers like when Priest was the front man?
Overall, its hard to pick betts in this poll.