Funny you should say that. I've heard a lot of people say they felt the Vortex has better glass. I've had both my 4-20 H591's alongside a couple PST's (both were 5-25) and it was pretty much a dead heat. And we spent some time between several people looking at a couple different objects.
But I do recognize that in the past there has been some variance in glass quality in some of the Burris. Some people have said they have great glass, and others felt it wasn't so hot. I suspect both optics have very useable, functional glass, and the difference between them won't buy you a hit