First, I'll say that I'm not a fan of the Sigma, (at least in .40), but that's purely a personal preference. That is the only one on your list that I have any experience with.
I'm a big fan of versatility. I LOVE the concept behind the Sig 250. One of my goals is that I want to be able to fire as many common calibers as possible. Never know when the next ammo shortage will hit, and what will or will not be available. Being able to switch between frame sizes is another great feature. That would allow you to experiment with different carry methods.
That aside, If you truly like the USP above and beyond all the others, and you can swing the cost, I'd say it's worth every penny. As for size, you must consider how you intend to carry. Obviously smaller guns hide easier than larger. But it doesn't really take much to hide a full size frame. It all depends on your holster and attire. Learning how to move without printing helps too. My daily carry is a sub-compact Glock, but I now wish I had just gone with the full size, as I am certain I would be able to conceal it just as well.
Just go with your gut. It knows you best.
The two enemies of the people are criminals and government, so let us tie the second down with the chains of the Constitution so the second will not become the legalized version of the first. - Thomas Jefferson