The Blackhawk is single action only, meaning you have to cock the hammer everytime before you shoot. I'm pretty sure the S&W is double action, meaning all you have to do is pull the trigger.
That may be important in your decision. Especially if shooting at a target or threat multiple times is important.
On the other hand, I think Rugers cost is considerably less than S&W.
If you want protection, I think I would lean towards S&W.
If you want a fun shooter with a western look to it, I'd go with the Ruger. The Ruger is definitely a hardy, trustworthy gun.