Should i trade marshawn lynch for steven jackson?

Why would you trade a quality running back who plays for a team that relies on the run game (The Bills) for a running back that plays on a scrub team that will be down 21-6 every week at the half and has to resort to the ping game to catch up? Lynch will have 100 more carries this season just due to the fact that Buffalo is so much better than St. Louis. Odds alone with that say keep Lynch. Cheers.