Let me suggest against the USPc .45 as a contender, for only one reason: greatly decreased capacity in the compact frame.
The full-size USP .45 holds 12 rounds, the .40 holds 13 rounds. The compact versions of those hold 8 and 12, respectively. So basically to get the compact frame, in .45 you give up 4 shots and in .40 you give up 1 shot.
Lots of people have a preference for certain calibers, I've made this exact argument before in other threads and I'm really not trying to go there. Whatever you believe about the comparison of .45 to .40, the two rounds are at least in the same ballpark in terms of performance. When the .40 compact holds 50% more bullets, to me that's a distinct advantage. All other things being equal: shooter skill, accurate controlled fire, etc, I think the greatly lowered capacity of the USPc .45 over the .40 and 9mm is a big knock against it.
How the gun feels should be the first consideration, definitely, but if you like the USPc and you don't have a caliber preference, let me suggest against the .45.