Eric, I have this scope - the Vortex PST II 5-25x50 FFP with the EBR-2C Mil (MRAD) reticle. I received the scope several weeks ago but have not been able to shoot with it yet, I have been able to play around with it and compare it to some other scopes in my arsenal and also scopes that have been in my arsenal but that I no longer have. I began my journey about 6 years ago with my high end scopes being a Bausch & Lomb Elite 4000 4-16x50 and a Zeiss Conquest 4.5-14x44, my thought back then was that no one needed a scope that cost more than $500 and paying a bit more than that for the Zeiss Conquest was hard to swallow. But then I was introduced to Snipers Hide and the rest, as they say, is history. Well that history has taken me through thousands of dollars of scopes as I continue to be educated by the community, and educate myself and my eyes as I hone and improve upon my shooting skills. I realized early on that many people have many different opinions and the Snipers Hide community certainly has them as well, but what I've noticed, by and large, is that there are fewer unsubstantiated claims in SH than most other sites I've visited for shooting info, meaning you get the advice of shooters with experience. I then took this great advice from many in the community and compared that to my preconceived notion that "no one needs a scope that costs more than $500" and decided the only way to know for certain was to see for myself which was either a blessing or a curse depending on which way you look at it - a blessing for my eyes and a curse for my wallet.
Why on earth do I give you such a background, it is because years ago I bought a Vortex Viper PST 4-16x50 FFP in one of my very first scope tests. As part of that test I had purchased not only the Vortex, but also a US Optics 3.8-22x44 (a hot scope at SH at the time), an IOR (Valdada) 3-18x42 and a Bushnell ET DMR 3.5-21x50. My first round of tests revealed that all these scopes actually did a decent job but overall optical clarity went to the US Optics; however, for price and versatility the Bushnell DMR ran a close 2nd for my tastes. I also really liked the Vortex PST but since all my scopes doubled as both paper/steel and hunting scopes, there was another test I had to incorporate and that was low light tests and this is where the men were separated from the boys and I found that the PST really struggled in low light to give me clarity and detail I felt necessary for shooting in these conditions. So the Bushnell hung around for about a year and then I found a great deal on a Zeiss Diavari FL 4-16x50, considered to have some of the best glass of any scope (at least so I thought) which put the other scopes to shame in regard to optical clarity and soon thereafter I bought a Premier LT 3-15x50 which actually had better glass than the Zeiss, in fact, to this day the Premier (now Tangent Theta) reigns as one of the best scopes you can buy in regard to optical performance. Over the years I have shared many of my own test results with the community because I realize how difficult it is to obtain one, let alone several top tier scopes to compare and for those who don't want to go through the hassle of buying and selling scopes as a hobby.
You also mention that you prefer MOA and that is where I used to be as well, the biggest reason was because I incorrectly thought MOA = inches and MIL = centimeters, but the reality is that both are angular measurements and they just happen to be close to inch/centimeter, but thanks to the Hide I realized trying to calculate inches at different ranges wasn't all that efficient and utilizing ballistic calculators really helps in identifying not how many inches or centimeters to adjust, but how many MOA or MIL to adjust, what's even worse is there was a time when there were Mil reticles with MOA turrets and that just confused everything for me. I also learned that 1 mil = 36"/3' at 1000 yards, and 18" at 500 yards and so forth, these are common measurements for big game and I realize that Mil is actually more favorable for the majority of my shooting situations so now all my scopes are Mil/Mil scopes. That being said, there is nothing wrong with MOA and if you prefer to use MOA/MOA scopes then there is no issue with that as all competent ballistic calculators will give results in both Mil and MOA.
Now, after all that, to get to your question: is the Vortex PST II 5-25x50 FFP a "good" scope for the cost and my answer to that based on my experience so far with the scope is an emphatic yes. The issues I had with the previous generation PST have disappeared and the PST II appears to be a good low light performer. I also like the reticle on it and think Vortex did an excellent job with the PST II as glass appears better, mechanics are really good and getting rid of the illumination tumor (hint, hint Schmidt & Bender) was also a nice touch. I've also had the Burris XTR II 4-20x50 which falls right into your price range and I'd have to say that scope might have a slight edge in optical clarity, but suffered from a bizarre optical aberration that I called "radial distortion" which Big Jim Fish summed up nicely in his
review of the scope where he writes "As the user moves his head around in the eyebox, he will note different parts of the image coming into and loosing focus." and I found that when my eye was positioned right the image was great but when your eye position was wrong it made you feel like you needed glasses at times, in lieu of this, while I liked the scope in general, for me it caused too much eye fatigue. I do not experience anything like this with the PST II which is great news but do want to get more time behind it to make a final judgement. The next scopes I would put in the upper end of this price range would be the Bushnell ET DMR but at only 5 mils per rev and no illumination along with it's heft at 34oz kind of put's it in a different category, but I'd say this is a great optic for a gas gun like an AR-10. I also have a Bushnell ET LRTS 4.5-18x44 scope which has impressed me at every turn, the glass in this scope is really impressive, I would say it is definitely better than the PST II, the DMR and even the DMR II (which I also have at this time) by a slight margin. What I cannot speak to with the PST II is it's mechanical reliability as I've only recently obtained it and just mounted it to my 17 HMR "trainer" and finding time for the range of late has been more difficult.
Hopefully this helps you with your thought process as well as give you some other options with scopes in this price range.