It depends on your scoring system. Collins can get you the 300 yards. Until last week he had 5 straight games with 300+ yards.
This week tho, I would play Stewart.
Not just because I'm a Steeler fan, but I am high on Stewart this year. You can expect a big game from him and Pittsburgh after an 0-2 start. The Steelers are pissed and I feel sorry for Cleveland.