HK on face value is higher priced gun than what you're putting up for trade, but it depneds a lot on the HKs condition.

I have a USP .40 LEM and a Glock 22. The grip on the HK feels like it has a thinner profile to it than the grip on my Glock or even my other double stack pistols (Taurus PT100, S&W 3d generation). The trigger reach, however,seems noticeably longer. My hands are by no means large- they are certainly not meaty (rather slender actually) but my fingers are on the longer side. I can shoot the HK like a machine. Same with the Glock. When I hand other people the HK, particularly people with smaller hands, they have serious accuracy problems. While part of it is learning the LEM trigger that mine has, it is undeniable that the shape and fit of the gun plays a role... I spent a lot of time dry firng my HK before I hit the range with it took hours of practice to get used to the feel. It still took me half a box of live-fire before I really had it down. The other semi-auto pistols that I have are much more intuitive- I took my Glock right from the show-room to the range and had it down within a magazine. My 3d gen smiths and Taurus were "on" for the first shot. Same with my Star PD. My 1911 had a bit of a learning period but was easier to learn.
All of that said, the USP is a great pistol. Fit and finish are excellent. Mags can be pricey, but there are deals to be had on quantity purchases of police trade ins and sometimes 10 rounders (full cap is 13). I haven't had any problems with the plastic mags- though there are metal ones available. The trigger guard is nice for gloved hands. The slide lock/release is either perfect or oversized and way too long...depending on how you like it (if you use certain holds, it is possible to keep the slide from locking or to unintentionally drop it). My USP came with a factory light. I really don't care about lights and I dislike frame rails. (The HK and Glock rails are very non-obtrusive and don't mess the lines of the respective weapons much) The recoil impulse is noticeably different when the light mounted. Even though the actual recoil is about the same, you can feel the slide movement more without the light mounted. That makes sense because the HK slide is relatively large and heavy.

If the USP is in good condition its is a more valuable gun, I would make that trade.

You didnt mention but it has been assumed, it is a straight trade or do you have to put anything on it?

Yes, even trade.

solid trade, IF youre not using the MP