I have been using magnified optics almost exclusively since around 2007. Back then I quickly discovered that if I could see something I could generally hit it, but if I couldn't see, or could kind of see it, my chances of hitting it was a lot lower. The only time a RDS gets the nod these days is when I am trying to keep weight and size to a minimum, and or the gun it is being put on is small itself. Back then the idea of putting anything but a RDS on a carbine was pretty much crazy talk, except for the Short Dot. As money was tight in those days I got the optic I could afford, which was closets to it, which was a Leupold Illuminated (pre-cursor to the VXR line). That scope has been on a lot of rifles over the years and is still going strong. Its circle dot reticle makes holding over a bit problematic as their is no reference for vertical or horizontal. Fast forward a year or two and I wanted more magnification on a scout setup than 2.5 could give me, so I put a Burris 2-7 on the rifle. I took a class with that scope and a conventional mounted 1.25-5 switching out. I discovered that I wasn't any slower at 2 than I was at 1.25. In fact I was actually faster at 2. I think in part that was the placement of the optic. I also found that while the difference between 1.25 and 2 was not significant the difference between 5 and 7 was. I have been told that the human eye can't tell the difference between .5x-1x depending on the person. I have also been told by folks who are a lot better with a gun then I will ever be that they are slower at 2.5 than at a 1x. That being said until recently both of those guys used a 2.5-10 for everything general purpose. I think it comes down to an individuals eyes and their shooting capabilities. For me the different between the low end doesn't matter, but the high end does, so I prefer these days to have a higher end and 2 on the low end. The exception, again is due to size, and that is most mpvo have a forward bell whereas you can get lpvo that don't have one. The extra length and difference in weight distribution does matter. To sum up I prefer a 2/2.5 to 10 or 12 or whatever I can get provided other stuff isn't sacrificed.
What I find way more important than magnification is the quality of the glass and the eye box. I ended up pulling the burris 2-7 off my rifle after a hunting trip. Evan had a 2.5 on his rifle, and I discovered in the field under various lighting and backgrounds the better quality of the Leupold 2.5 made it easier to see things. The burris worked, but the Leupold worked better. At this point I optimize for the best quality glass I can afford. That being said I think that the Leupold X3 and VXR line don't get the credit they deserve. They have good glass for the money, and I don't think anything in the same price range competes.
When I shoulder a scope and run through the power range I want to the reticle to be right there in my field of vision. I don't want to have to hunt for it, or hold my head in the exact right position. That all assumes I mounted it correctly. I have found that I had to slide my head a bit further forward at full magnification if the spread is wider to get the best clarity, but that is leaning into the rifle a bit more something I end up doing anyway when prone, kneeling, etc... so having my head slightly more upright standing and lower power seems to work out anyway. I personally don't like either of the new NF 1-8s for that reason. They have a very tight eyebox and I found myself really fighting to keep my head in the correct position. I have that problem actually with a lot of the 1 to 6/8s I have looked at.
SFP/FFP - For me it is easy I have never looked through a FFP that I liked the reticle on, and never had a problem with SFP. Perhaps I am just not shooting far enough out to make a difference, but for me I will take a SFP. Yes I think the reticle gets to small at lower magnification, in the field (only looked through other folks scopes never used one) that makes it hard for my eye to focus on the reticle and not the target. Again maybe just and issue with my eyes.
Daylight Illuminated reticle - Yes I am a huge fan, but prefer just the center of the crosshairs or a center dot to the whole plex being illuminated. That being said if the scope has all the other features I like then I am willing to sacrifice a this feature after years of not having it.
In my experience the simpler a reticle the better as I tend to get lost in data overload with the more complicated reticles. However, again I am not a long range shooter or shooting movers. If I was to go down that road I would probably use one enough to decide if it was going to work for me or not. With the shooting I do, I don't feel I am missing out, but it is truly a case of not knowing what I don't know.
Weight - I think this is an issue to often overlooked. On paper the Razor HD is an awesome optic, looking through it awesome optic, but as soon as it gets on a carbine it overpowers the handling of the rifle. It is simply to heavy and makes the rifle to awkward. For years I stuck with 16oz or less, and preferred less than that when possible. I still do, but when it comes to ARs, I have found I can go to a 19oz scope and a fixed mount and be roughly the same weight as a lighter scope in a QD. There are trade offs, but so far I am happy.
As I said previously, I think that the Leupold VXR line is a best buy. I have multiple of them, and that would probably be all I had without friends and hook ups.
The current goto scope for a lot of guys is the Steiner, as it is lighter than the Razor HD, and performs well. If you have more coin definitely worth a look. I haven't personally messed with them, but they get very high marks.
Razor HD, for years that was the go to within the .Mil world for lpvo, and if you can get over the weight then worth a look. You can usually find a deal on them as folks buy them, don't like the weight and sell them. My only complaint in the time I have messed with them is weight.
As El Mac pointed out the Sig Optic, two if I am not mistake, were recently choosen for different programs. Based on that worth a look, but I have no personal experience. El Mac if you do please post about it instead of just a link.
Now my personal current favorite GP scope, and I only got to try them do to a friend is the NF 2.5-10x24. In reality it is old tech, but I understand why it has the cult following it does in the .Mil and LE circles. They only boxes of mine it doesn't check are weight, which I deal with by going to a fixed mount, and the daylight visible reticle. I am willing to sacrifice that because I just like the optic so dang much. That being said I don't have a problem using a Leupold, I just have the opportunity and money to afford the NF.
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"If anything goes wrong it will be a fight to the end, if your training is good enough, survival is there; if not nature claims its foreit." - Dougal Haston