I have owned several Glocks and still have a G23, and have shot several HK Usps, and own both P88s and P99s.
Folks seem to either love or hate Glocks; personally I feel life is too short to waste time on the powerful emotions of hate so all I can say is they are not my cup of tea. Even after having the gun worked over, my G23 is only a fair gun. I don't like the grip or the angle, nor do I live the trigger feel. The mag release is primative at best. It is boxy and ugly, and worth all of say 350.00 dollars to me. (And no don't bother flaming by offering me money for mine, it is good for taking in the fishing tackle box, I have not guilt about a Glock shifting around in two inches of water in the bottom of the boat!)
Problem is Glock now encourages dealers to sell them at more like 600.00 dollars with puts them in a catagory of being compared to others in the same price range.
The Usp is a disapointment IMHO. Here is the company that produced such greats as the P7 series, and I expected as much out of thier polymer gun. Instead all I find is a price point to try to counter the hard mark to dollar exchange rate. The trigger is mushy IMHO, and it boxy in design, with little inspiration. The safety, while clever in it's flexability fails in pratice for fit and feel. It is hard to imagine that this is produced by the same folks who built my MP-5.
The walther does not walk on water, it is not the perfect answer, but it is a pretty cool gun. The first shot pulls forever, but is at least as manageable as a glock. It at least does have a clear take up and release, and the second shot on release point is clear and great. The design is nice, the angular slide reminds me of the Jericho with it's triangle like design. This produces a top of the slide that is more narrow, and encourages better siteing in on shots. The grip is outstanding, and flexable with the back straps. With the high caps you can get on the market, you will have 16 rounds of 9mm. If you can accomplish what you have to in that number you have a problem. It feels good in the hand, aims well, and triggers well.
My experence of walthers tells me that they can be load and shape sensitive, but the P-99 feeds hollowpoints and 115 grain bullets better than any other Walther I know. Try loading a light hollowpoint into a PPK and see how it feeds when you are counting on it- No Thanks!!
So the winner IMHO is the P-99, good grep, decent trigger, and natural site window, and cool looks to boot!