I bought my FA 475 from a friend who felt I needed one and helped me a lot, I really like the gun. Now it came with a 480 cylinder as well, something I would never order with the gun but in reality probably is a better fit for the gun for a couple of reasons, A: you can shoot pretty much and hard cast 475 bullet out there, B: you can push the 480 to within about 100fps of the 475 so it is in a power range that will rarely be used.
In the real world I have ordered 2 different LBT molds that were cut to fit the 475 cylinder so that has not been that big of a issue, if you want to order standard 475 molds it will matter as the RCBS and the Lee 400gr are both a little long for this cylinder. Now I have both Bisleys and this FA and the biggest difference I have noticed with the grip frame is the FA has "ears" at the top of the grip frame like a Blackhawk does. I have had the grip slip in my hands and cut the web of my thumb with heavier loads, something that can not happen with the Bisley.
Given a choice I would probably have Bowen build me a 4 5/8" (not the standard 5 1/2" with the barrel band) Nimrod in 475, blued, casehardened frame, custom grips, the whole works. Now that package would set you back probably $3000+ the base gun. So with that in mind I think the approx half of that that I have in my FA is a great bargain, especially for my first serious big bore. The rest have been slightly tuned Rugers that are a far cry from the guns we are speaking of here.
So all of that being said try to shoot both guns first and buy the one you like the best. If you can not get your hands on any (like was the case for me) a used FA is the best value out there. Buy it shoot it, and upgrade if you want then you can sell it for at least what you have in it if you look around. Fun game to get into though...