Hey, if he was in special ops he wouldnt have asked the question. :)
Seriously, both the SIG and the USP are good guns. Standard issue stuff, but reliable.
High End($800-$2000): If you want to use what the pro's use, take a look at some of the models from Wilson Combat(
http://www.wilsoncombat.com/) or Kimber. These are the real deal, and are priced accordingly. Also, check out the Springfield "Operator" model. Very nice for a production gun.
Medium cost($400-$800): SIGs, Glocks and HKs are all reliable and accurate. Lots of aftermarket accessories are available.
Remember, a gun is only as good as the person shooting it. If you dont spend time at the range, that $1500 custom gun isnt going to do you a bit of good.