I don't have a USP 9C, but I have a USP 9, USP 9 Tactical, USP 45 (two actually), and a USP 45C. I also have a VP9. As a carry gun,I prefer the P30 to all of those, except maybe the USP 45.
For the two you asked about, they are completely different guns. The VP9 is not really all that different from a Glock. The trigger is lighter with a more crips break in my experience, and it has an ergo grip if you like that. I like the VP9 fine but it rarely comes out of my safe.
The USP is a hammer fired gun with a modular trigger system. You can swap it from DA/SA with safety and decock, DA/SA with decock only, or SAO by just changing out the control plate which takes 30 seconds and is an $8 part. You can also put a LEM kit in it for what I think is the best all around carry trigger system. The only real drawback to a USP is that it does not have a standard rail. If you want to mount a light, you can get an adapter, but that will limit your holster options. I rarely use a pistol mounted light, so that is not important to me, but it may be to you.