I don't recall having evaluated the Leupold MK4 8.5 x 25. It would not be my first choice due to the high (25X) mag ratio. Glare performance at all magnifications gets worse as the magnification range increases. Glare performance is important because glare limits image contrast. Also, I prefer a lower mag than 8.5X on the low end. Otherwise, I like MK4 scopes and spotters.
I don't have a good sense of the Nightforce NXS 5.5x22 scope because the room lighting was poor above that booth at 2012 Shot. At previous shows I found the Nightforce optical performance to be average to above average for that price point.
I already commented on the Huskemaw 5-20. Optically, it's not in the the same league as either the Leupold or Nightforce. So there you have it. I guess my preference is for the Nightforce NXS 5.5x22, although it is heavy IIRC.
Which one do you prefer?