I did almost exactly as you are contemplating. I had the BH-55 for about two years. When I tested it (UNscientifically, mind you) side by side with my friend's Markins M20, I liked the lighter weight of the Markins, the smaller size, and it's drag was slightly better and easier to control. I did miss the extra drop notch on the BH-55 though.
As to the plate, I had the quick release plate on the BH-55 and was going to remove it to use on the Markins. No matter what I did I couldn't loosen the nut holding it on. I almost stripped it in fact.
So, I ordered the Markins with the screw tightener, or whatever you call it, instead of the quick release. I like it a lot, although it's easy to confuse the knob which controls the ball with the slightly smaller knob that locks the camera plate or lens plate in place.
me
. after almost dropping my 1ds mark III after accidently loosening the QR 


