Either one is a fine firearm.
The Blackhawk with adjustable sights will allow for the use of different ammo loads.
The Vaquero with fixed sights means that you might want to find a load it likes and stick with it or learn where it's going to print with each load change.
I'm curious, why .45 LC and not .44?
I don't think the Vaquero can handle .44 Mag, but .44 Special is such a joy to shoot. The Blackhawk can use both, just an option you might want to consider.