I honestly have not seen Rice play yet this year, but his stat lines aren't looking great. He isn't getting near the catches of last year and doesn't seem to be getting it done on the ground either. I have also heard his knee is hurting and McGahee is back to vulturing TDs. That being said, I have seen Mendenhall play. He has looked great, yes great, this year with teams stacking the box every down. When Ben gets back he should continue to put up good numbers. He is the also undisputed feature back, can stay in for 3 downs, and it doesn't look like Redman or Dwyer are going to take any TDs from him.
I would stick with Mendy, even though I am a homer.