I have never used a Viper PST other than firing maybe 20 rounds out of a friend's rifle with it, but have a VX-R patrol. I like it overall, but there are a few weaknesses. The turrets move very easily. Too easily. They are easy to knock off your zero when you don't intend to. They drag on anything, and they have moved. There is no indicator on what revolution you're on, and no zero stop - so you can get a rev off really easily. I actually put a small piece of duct tape around part of the turret to keep it from moving (since I keep it in a bag in my patrol car in a QD mount). It's ugly, but it works. If it had any type of zero stop, it would be a non-issue, but it doesn't. I really wish it did. Another thing is the small crosshairs of the reticle are too thick for really precise shooting with small targets. It covers up a lot of target. The one mil and half mil hashes are hard to distinguish from one another. Get in a hurry, and your holdover could be off.
It's not all bad, though. The lower turrets are better IMO. I don't want a turret sticking up an inch for most of what I do. The mil/mil is the way to go. I like the fact that it is SFP for the 3-9 mag range. In low light the thick reticle up close is easy to see, even without the dot on. That brings me to the dot. The dot on this thing kicks ass. It's almost aimpoint bright, and hard to turn on by accident. Numerous settings that I found useful from full daylight to just ambient light in town. Did I mention the dot is awesome? When the thick reticle is giving me trouble trying to shoot little groups, turning on the dot (which is smaller than the thickness of the reticle, BTW) and all of the sudden I'm cured. The firedot makes this scope. The magnification ring is much better than that of the Mk4s. The scope is realatively small and light compared the Nightforce I have on my bolt gun.
Although subjective and individual preference, I thought the glass, eye relief, and eye box on the Luppy were much more user-friendly that the PST. The brightness and clarity really stood out as much better, and the eye relief and eye box might just be what I'm used to. The PST I shot with was of a higher magnification range, so it's kinda apples and oranges.
The VX-R really needs a zero stop. It really needs the turrets to be a little more stiff (TWSS). The thin crosshairs need to be a little thinner (and honestly, at the same time the outer, thicker part could stand to be a little thicker, IMO). They'd have a great little DMR-type scope if they did those things for the same price point. I'd buy another in a heartbeat if they did.
I'd look through both before I bought one or the other. I wasn't floored by the view from the PST when I shot with it (it surprised me, since I had heard so much good from them). It may be fine for what you want.
