Howdy Boon,
The firing pin on the hammer is neither good or bad because, in CAS, we are only allowed to load five rounds in the revolver and must begin each stage with the hammer down on an empty chamber. Some foks claim that hammer-mounted firing pins are more prone to break when dry firing. If that's a worry, then use snap caps. But some folks also claim that revolvers with a transfer bar system (i.e.:Rugers) are prone to transfer bar breakage. So... take your pick.
I've not heard of a "Durango" pistol but I'd imagine that it's made in Italy. The Italian guns (clones) can be made just as slick as any, but they often require a bit more work to be made so.
But... before you buy guns, get yourself to a shoot near you and handle some that other folks are shooting. All you need to do is say exactly what you said here, "I want to get into CAS and I need all the help I can get" to the first person that says "Howdy!" And, believe me Boon, somebody WILL say Howdy!