I have the same decision, I am leaning toward Knowshon, but not totally decided yet. Both have pretty good matchups. I feel like cleveland is more likely to keep a close game with denver, as compared to arizona keeping up with chicago. As up and down as chicago has been its hard to guess what they will do. Forte is more likely to lose carries to another back, both should catch several passes. I say knowshon, but someone with some really good arguments could change my mind.
I'm leaning toward Knowshon as well. The one thing I was concerned about is him getting the carries, and he's gotten 20+ carries in each start, good enough for him to be a big producer. I actually think Arizona will keep it closer than Cleveland, but as long as the games stay relatively competitive I can see both producing. Tough choice.