I have the Blackhawk in 4 5/8", but I'd be super-happy to have the Model 58 that Doc Hudson knows about. (Those 58s are getting hard to find! Doc, I would email you myself but for the NIB .40 Hi-Power I bought last weekend!) If it were the other way around, I'd be super-happy to have the Blackhawk, too.
I personally don't feel either revolver has the edge in recoil. I think the Blackhawk is probably a little sturdier than the N-frame, and less likely to go out of time. I used to manage a gun store many moons ago, and it was not uncommon to see S&Ws loosening up more than one would like after a diet of heavy loads (very common with the .44 mags). I've never seen a Blackhawk with this problem. Robert's right, though, the Smiths have a much prettier finish, a generally sweeter trigger right out of the box, and are a tad more accurate on average.
As I said, these are both guns I'd like to have (and you haven't even brought up the elusive Ruger Redhawk in .41!). The .41 mag is a great little round!