I have all three, PST 4-16 on my wife's bolt gun, the SS 5-20 on my back up duty rifle and I run the new NF ATACR on my primary rifle. IMHO the NF if the best of the three, and I ran the NXS and F1 prior to going with the ATACR. The next is the SS 5-20, I picked up used here on the site and it is a great scope but does not have some of the features of the PST that the wife got from Mike @ CS, the only person I will by new from. It is a nice unit and less then $900 and is the least expensive option. With optics what you spend makes a difference BUT at some point intended use vs. price becomes a big factor. From what you have shared I would suggest calling Mike and grabbing the PST and save the difference on ammo and get some serious shooting in. After you have some experience your probably going to do what "all" of us have done and become a optics junkie and as funds allow buy more scope then you need. Trust me, over five years I have bought and sold about ten scopes. So start with the PST and shoot, shoot, shoot!
Sully