It usually depends on the bounce angle.  The lesser the bounce the better for sweeper.

MB has a bit more bounce from 3 to 6 but 7 to P is the same as CB. 

MB should be more for a digger but really not by much though.

Jeff,

The CB's have a wider sole than the MB's which will make them not dig as much than the MB's.  As a sweeper you can play either, but I would factor in trajectory in your decision.  The CB's will hit the ball a little higher.  My set make-up is 3-7 CB & 8-PW MB.  I like to be able to hit the longer clubs a little higher & also control the spin and trajectory more with the shorter irons.  If you hit the ball high will all of your irons then a full set of MB's will be fine.  But if your longer irons are not a higher trajectory and struggle stopping the ball on the greens with them then you may want to consider a combo set or the CB's.  Your seeing more Tour players go with CB long irons and MB middle to short irons in their bag.  Hope this helps in your decision.  Best of Luck!

Thanks!! I appreciate the input!!