I have the same problem in one of my leagues (but in a 12 team and we only start 2 RB's).....I have Forte/Jacobs/Ward.
I have been reading alot on Rice and most people seem to favor him. I personally chalk this one up to personal prefference and gut feeling. Rice will start and is atop the depth chart with McClain as the FB (but will still get a few carries like M.Alstott use to do) and McGahee at alternating. Ward on the other hand has Graham and Caddy! Now we all know Caddy will be done anytime from week 1 to a few weeks into the season and so Graham will only be there to spell Ward! I see the whole TB situation coming to a fast end before it begins.
They will notice that the real RB in TB is Ward and they will give him the majority of the carries (if they want to win games) until the injuries pile up to Caddy and Graham.
Personally I prefer Ward over Rice just because Playoff time comes they have a super easy schedule and personally I think Ward has more explosivness if given the chance. Plus I think Baltomore passes more this year (so far in preseason it seems that way and they are letting Flecco loose).....this does benefit Rice more since he is great pass catcher out of the backfield but your not in a PPR league.
I say if you can wait anywhere from 1-4 weeks for Ward to take over the full load then it will be worth it and I think he does better.
Either way you can't really go wrong though.
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF