The Blackhawk, SBH, and older Vaquero's are built on a larger frame with a larger cylinder. They are the better choice if you want to load up heavy hunting loads. I never really liked them because they never really "felt right" to me.
The new model Vaquero is built on a smaller frame that much more closely feels like the original Colt SAA and is my preference. If you want to load 45 Colt up to near 44 mag specs you really need either the 44 mag or an older model Vaquero.