I'm going to possibly stray from the path a bit. You already have a pistol, right? How many quality training courses, not including mandatory CCW courses, have you taken? If you have a good training background, how long ago was your last training? Quality training will trump having another pistol to rotate in your daily carry routine every single time. Just a thought. A lot of people get too fixated on the gear and don't focus enough on their own skills, myself included a lot of times.
That said, I don't like the grip on the USP. Love the P30 grip, though. I'd take a Glock or M&P over a USP any day of the week, however. It just doesn't fit me well, plus I don't care for safety levers or the trigger. Same goes for the P30 when it comes to the trigger, but at least the grip makes up for a lot in my hand. Make sure you hold one and see how it feels before deciding.
"Intelligence is nothing more than discussing things with others. Limitless wisdom comes of this." - 山本 常朝