As has been said before in the thread, both very fine gentleman and both make very fine rods. I am fortunate enough to own multiple rods from each.
Gary has a little more of a niche in the super-light, trout spey area. Bob has more diversity of actions, and more stuff in the longer, heavier categories. My own quiver is disproportionately ACR in the lighter rods, Meiser in the mid-weights. B&W for the heavy artillery. That said, heaviest fish I've landed on a swung fly, a Chinook in an unlikely time and place, was on an ACR rod. Go figure.