I have. I've even had them side by side.
I'm not a fan of the NX8. I dont think it really hits on all the points I would expect in a Nightforce product. I think it works fine as a hunting scope, but for a competition optic, the eyebox is too tight, the DOF is too shallow, and the parallax is too finicky. You can often take the time to deal with that while hunting and set it for the one range you are shooting and be done. But the glass falls short for me as well. It looks brilliant in the middle, but the edge distortion while transitioning or panning is noticeable.
For me, that excludes the NX8 as a purchase option. Especially with so many other quality optics at that price point. I will add that I do like the 32x versus the 20x as the glass distortion only seems to occur closer to the edge.
I do think the Leupold is the better option. I have seen a couple of the 25x that weren't brilliant optically. They had a yellowish tinge to them that made them seem less bright. But I've looked through some that were pretty good. I've looked through one 35x to date that I was comparing to my 30x XTR3 and 35x ATACR. It seemed decent to 30x, but suffered some after that.
Of those two options I would take the Leupold.