ameyers, the BBS drag is a off-set "rulon" disc drag. The mid-arbor is a center line drag with a composite surface designed to give the feel of a cork drag.

Each reel uses a different bar stock aluminum composition. The composition of the BBS aluminum is a bit lighter then the mid-arbors.

Both great reels. BBS is a little lighter then the mid-arbor, mid-arbor's drag is stronger and also has the advantages of a larger arbor which have been pointed out.

For the money you cannot go wrong with either reels. Rob