Cadillac Williams or Brandon Jackson?

Do I roll the dice on Cadillac as my number 2? or stick with Jackson. Caddy has the great Pitt D while Jackson has the Bears. I sense Jackson will have a breakout game one of these weeks but hard to ignore the fact Caddy has 20 plus touches a game and he will break out soon too, and Jackson looks like he's in a RB by committee. Thoughts and ideas much appreciated. My 4th back is Beanie but obviously he's hurt so hes stashed away. No real decent back to pick off of waivers as i'm in a 14 team league. Pierre Thomas is my number one back.