Well having owned a USP with one of the early triggers, I can suggest the following things that would improve your performance on anything shooting fast.
-Reciprocating mass... The USP slide is stupidly heavy.
-Bore axis.... the usp bore axis is fairly high.
-Barrel lockup... unless you get one of the USP variants with the o-ring, the M&P seems tighter on average. this may be a push over a large enough sample, but between the handful of M&Ps and USPs
-recoil springs. The dual stage springs in the USP make the sight track funny and probably take longer to return to a meaningful sight picture.
-The mag release can be awkward for a lot of people, whereas the M&P release is easily reachable by most people. So shave some time off reloads.
-DA first shot. The USP's DA pull is fairly horrendous. Even stock, the M&P likely punishes you less on the first shot. And doesn't lose all that much to the SA follow up shots if you are focused on getting through the stage.
I sold my USP a while ago.. built like a tank and reliable, but just not a fun gun in the end.
