I would say, having owned both, durability and repeatability will definitely be better on the uso. Glass will be a toss up. The mk 6 has elevation turrets that take some getting used to. The uso will have a great amount of options available so you can get exactly what you want. The ereck knob is really good (in my opinion). With the leupy you get what they give you for the most part. For an extra grand you can get illumination. Don't get me wrong, I like my mark 6, but I got it largely for it's wt. and size since it is on a hunting rifle.