I've got 3, VX III and I'm happy with all of them. Buddy of mine just put a VX II 6-18, with the CDS dial, on his 7mm and I thought the glass was pretty good for the price. We shot it out to 780yds and it seemed to track fine, what little I used it.
Now I know there's a lot of people on here that like the vortex's and I don't have a lot of experience with them, but the one 6-24, PST I did look through was bad. It was very cloudy around the edges, and it wouldn't get clear. Probably one bad apple, because theres a pile of shooters that love them. But the same guy has a couple of Mark 4's, 6.5-20 and I think the glass is exceptional on them.
I've got one sightron SIII 6-24 that's waiting to be placed on 6.5x284 that's looks **** clear. I thinks its clearer than my VXIII's, but it's really hard to tell until they get mounted and you start using them. I wouldn't hesitate to buy another sightron SIII. I also wouldn't hesitate to buy VXII for moderate ranges either. For the most part you get what you pay for.