Looking at yards rushing alone you can come away with caddy being better.
However, Caddy was not productive in two games, and his size may be a reason he is already dinged up. He reminds me a lot of C. Garner who was a similar size and would show great burst and rushing skills but then would get dinged up and be out for a few games here and there which limited his overall production.
Also, I just dont see Carnell making that block Ronnie made against the Bills DL in pass protection (on the long booker pass play) Ronnie looks like he is a lot better in pass protection than Carnell.
I also think RB has better hands than Carnell and is more effective coming out of the back field (however Gus and our play calling don't go to him nearly enough)
When you factor EVERYTHING in, RB stands out as the better overall running back.