Both are nice "gentlemen" knives--small blade, light-weight, and made with high-tech materials. In "fit and finish," I would give the nod to the Wm Henry; however, I personally prefer the BM 770 (I'm assuming you're talking the carbon fiber handled version--not the aluminum handled 770). The boron carbide coating is sweet and is not a common option on most knives. Further, the 770, imo, has more "attitude" than the Wm Henry. Osborne knows knives!
Bottom Line: If you want a looker, get the (baa baa) Wm Henry. If you want a user, get the Osborne.
P.S. I have a MOP Wm Henry that has sat in my collection case untouched by human hands for a number of months but that's another kind of knife from what we're talking about here.