US Optics and Leupold make top tier glass without a doubt. My buddy runs a USO 1-4 and I have had a bunch of time on it. Scope is built solid and tracks perfectly if you have to dial. I currently have the MK8 1-8 and love it, but wouldn't think twice about buying a USO scope if I needed another. Whichever you can get the magnification, reticle and knobs that suit your needs, at the best price would be the solution. No bad choices there.
I've heard several reports of the USO having distorted glass, eye box also is not considered to be great and field of view is mediocre to poor. I'd take a Mk6 all day over the USO, it's a known quantity and I can verify it has great glass but in the price range you're looking in, Kahles K16i SM1 is the best glass available, stupid forgiving eye box, gigantic field of view, daylight super bright reticle, mil based stadia, lightweight, .1mil adjustments and even allows storage for a spare battery, you literally cannot go wrong with it.