A mate of mine has both the 4-16 PST and the 6-24.
He was considering getting another 6-24 instead of the 4-16 he brought for his AR15. He was glad he got the 4-16, as you wouldn't want a much bigger scope on an AR I'd say, unless it's solely a bench gun.
We compared his 4-16 PST to my Nikon Monarch 4-16x42 and surprisingly the Nikon was better in low light. When I say low light I mean until you could barely make out a target at 100yards. That despite has a 25mm tube and a smaller objective, which makes it a lot lighter and smaller.
The Nikon doesn't have target turrets, but does have capped turrets, and you can buy exposed turrets for them I believe. Don't know if this info is any help or not, but someone had to give you something to think about.