The Scandium adds a bit of elasticity to the aluminum alloy of the frame, but their wear properties are very comparable. With a cartridge like the .45ACP, I doubt you'll see much difference in wear between the steel, Sc or Al frames.
If you are looking at a S&W 1911, take a look at the new (I think they are called FE) models. I believe they have done away with the grip safety FPB and gone to a light firing pin...like Springfield Armory.
While I have never had a problem with my 1911Sc since I bought in new in 2005, the external extractor used on the Performance Center 1911s are superior. As a matter of fact the PC 1911s are more than just a tuned production S&W 1911. Compared to the Springfield line, the PC 1911s are more like a Professional than a TRP