The stainless model of the New Blackhawk has a stainless grip frame. The Blue model has the Aluminum grip frame. They can be interchanged with some fitting.
Gunsmith and hunter John Linebaugh has done a lot of work with the Blackhawks in .45 Colt. He has load data with pressures up to 32,000 CUP, and thinks that the heavier bullets and larger calibers make more effective hunting handguns than the higher pressure magnums, while being nicer to shoot.
See:

Linebaugh's Custom Sixguns - The .45 Colt - Dissolving the Myth, Discovering the Legend

for some good reading on the subject.

Best,
Rick