What you won't get is the durability, the ability to take insanely hot loads
and the transfer bar safety.
For SASS shooting, I doubt any of that would matter. My understanding is that most of the better Italian SAAs (especially Ubertis) shoot standard-pressure .45LC accurately enough for SASS duty right out of the box.
My next gun will be a Blackhawk in .357 with mods. I expect it'll be able to handle 158grain loads pushed past 1,500fps, maybe more. In terms of muzzle energy, that puts you at the low end of .44Mag power levels, at least at the muzzle, while maintaining the flexibility of running milder .38/.38+P/.357 personal defense fodder.
.357s that hot can kill anything in California, including Black Bear and boar. I would NEVER trust an Italian SAA at those pressure levels...but then again, ballistics like that have no business being anywhere near a SASS match.