While I would hesitate to recommend a 1911 and full power 230gr loads to a new shooter, I think the lighter .45 ACP loads in a gun like the USP compact are no more difficult to shoot than .40/.357 Sig. Not that you couldnt shoot the full power stuff if you wanted to. The H&K semi autos that I have shot or owned would function on any ammo you put in them.
If its on the DOJ approved list, the USP compact in .45 ACP makes a lot of sense in CA since the citizens there are still limited to a 10rd capacity. Its a slightly bigger gun than the 9mm/.40/.357 version, but its only noticeable when they are side by side. The 8rd magazines are also steel for the .45 compact instead of polymer like on the smaller calibers if that mattters. Neat guns.