I have a P229 9mm and H&K USP compact in 357sig.
Both are excellent. I would recommend either.
Comments that might help you:
My Sig is one of the older ones, made in Europe, and so has been incredibly reliable and just worked and worked with never any problems. Magazines are not cheap (but are now much cheaper than they were during the Clinton years).
The new Sigs are made by Sig-US, NOT the "real" Sig company. I don't believe that they use many genuine Sig components any more. The result is that I do not believe that a new US made Sig is anywhere near the quality of the genuine European manufactured Sig. They seem more interested in the bottom line than in manufacturing high quality firearms. Of course, their contract with Sig means that there is no way you can get your hands on a new EU Sig to make a side by side comparison. However, for a US manufactured gun, they are still pretty reasonable.
My USP just works also. My biggest complaint is that even now I can't easily get hold of the full capacity magazines. This is an indication of the problem with H&K -- they have zero interest in the US civilian market. its up to the various importers to pick up what they want, when they want. So something like a less common caliber magazine can be hard to find. I do wonder what the spares situation will be like for older models down the road.
You mention that you want to be able to cock the hammer - well, the Sig is better in that respect because it has a "normal" hammer. The hammer on the USP Compact is "bobbed", the spur removed to prevent snagging on clothes, making it much less easy to cock.
However, the USP Compact also has a safety -- which the Sig does not, which makes carrying the USP "cocked and locked" a possibility -- you get the choice: DA with the harder pull on the first shot, or using it as a SA, carrying C&L. What you probably wouldn't want to do anywhere but on a range is fiddle trying to get a grip on the hammer to cock it for a first shot.
Really you can't go far wrong with either, and you will learn to live with either pretty quickly.
I carry my Sig on a daily basis -- but that choice is really determined by the availability of full-capacity mags for it, and not for the H&K more than anything else.