IMO the usp shoots better than the p2000. I think it also feels better. Both good guns. If I hadn't of picked mine up so cheap I wouldn't have ever bought an h&k. Which I'm trading mine for a 9mm glock and then I am swapping that for a .45 xd compact.
I would say go the the usp. But then again I will tell you to get another m&p...but that is only my personal opinion. I hope you are happy with whatever you get.
Oh iirc I think it was easier also for me to find stuff for the compact usp than the p2000