I have the vortex razor HD Gen2, and my cousin has the PST Gen1. I can tell you now, that their is zero comparison from the Razor to the viper PST. The Razor completely blows it right out of left field. The PST is a great scope, and comparing it to the gen2 PST, I don't see much of a difference other than a few mils of elevation etc etc on the gen2 PST... Not much to really warrant a few extra bucks on a new market PST Gen 2.
If you have the money to throw on a razor hd, get it! You won't be disappointed. I have it mounted onto my 338 Lapua cadex with spuhr and couldn't be happier. The PST is also a great scope if you can't afford the Razor! Hope this helps!