I have 10k rounds through my HK USP40 fullsize and it has never failed me. It's never had a jam, FTE, FTF, ect. Not so much as a hiccup from this gun. I've fed it cheap ammo, expensive ammo, hollow points, FMJ, steel cased ammo, ect... it has ate everything I've fed it and asked for more. I would bet my life on this gun! My HK is very accurate, and very reliable. I love the ergonomics of the HK. I agree with Zen, all other guns should strive to be HK in the combat pistol world.
My dad has one of the first USP's made in '93 and it has just over 50k rnds through it. Never a jam or FTF or FTE. And after 50k something in the trigger mechanism did break, HK's awesome customer service, and lifetime warranty, took over and fixed the gun, no charge.
I've held the P2000, but I just bought a P2000SK as my concealed gun for my business. I love the way the P2000 feels. I love it's slim design, and I like the decocker on the rear. What I don't like is that there is no external safety or a trigger safety. I figure it should have one or the other. If I were in your shoes, I would go with the USPc. You'll like the safety/decocker if this is you first gun. My HK USPf 40 was my first gun. Even after buying a Ruger Vaquero, Kimber 1911, and a Beretta, my HK is still my favorite... it is also my go to gun.
In the end it really doesn't matter what any of us think. It's what you think. Go to an indoor range, rent an HK, rent a Sig, rent a Glock, rent what you can. Shoot it, and decide what you like more. When looking for my gun, I shot many many guns. And finally decided on the HK based on ergonomics.
Let me step up onto my soap box here.... HK's are not overpriced as people on the internet would like you to believe. People hear this then repeat it. Given a comparable Sig and HK, you will be within $20-$50 of each other. I posted this in another thread: There is a common misconception that they are overpriced. They aren't. Lets compare it to the Sig. I used Buds Gun Shop to search for price. And you have to compare apples to apples, so I'll compare the HK USP40 Compact and the Sig 229. The HK cost $673.68, whereas the Sig cost $651.43. For a grand difference of $22.25. There isn't a big different between the two. Now, with all that said. You have to be a good shopper. Markup is a bitch, some places will mark up certain guns more than others.
Here's my HK after a trip to the range: