I think they are higher quality than your standard Ruger single action and as good as the X-frame Smiths. I think you will find them easier to shoot/handle than a Ruger SRH.
I have a 475/480 and so far have been pleased with it. I just got it in the latter part of the of last year. My choice would be one in 475/480 or 500 JRH. The 45/70 should not be too bad to shoot and it was the very first BFR offering.