I think the main advantage to a mag, is not having to break position for another shot. However, it's debatable, because I suspect many, if perhaps all, lack a position that is sustainable without breaking anyway.
It was just a toy i saw and thought "oooh, i'd like to have that for having fun with the racks" rather than exploring a possible advantage...
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep