First off, I really just don't see how Bush would perform better than Turner this year. IF Bush can stay helathy, and that's a GIGANTIC IF, then he's still going to have to get 1400ish yards and score double-digit TDs. With the TD thing the way it is and the fact that you start 2 RBs, why give up two sure things (or as sure as you can get in fantasy football
MJD and Turner are for sure top 5 RBs in almost every ranking I've seen thus far. While AJ is my #1b WR right with Randy Moss this year, he's still not getting picked until late 1st-mid 2nd rounds... while Turner and MJD are off the boards within 3 picks most times.
Think about this... if you were to not "keep" one of them two who do you think will be the first overall pick in the next redraft? Yep, probably Turner.