Hi folks -
So I ended up getting Gitzo 3541XLS legs and a RRS BH-55 (with the lever release). I also ended up getting L-plates for all the cameras and collared lenses.
I have to say that I love the legs, and I'm happy with the ballhead, especially the L-plates and quick-release system in general (despite my initial misgivings).
I have noticed that the knurled knobs on the RRS head are kind of tough on the hands, and might be a problem in very cold weather particularly. I've also noticed that with drag set on the head, it doesn't move nearly as smoothly as I had expected. Not a problem for me, as I prefer not to set drag and just loosen the ball instead.
I have noticed that when using heavy, non-collared lenses (like the Canon 24-70mm f/2.
that the BH-55 does droop a little after tightening if the lens is pointed down. Not badly (maybe half a degree or so), but I would have expected no droop at all.
I don't know if the Markins would be different in these areas (drag smoothness and droopiness), but it's not enough of a problem for me to consider ordering an M-20 and possibly returning the BH-55 - I'm quite happy as-is.
Thanks for the feedback.