My AT-X in the back, my buddy's SMR in the front. He left his rifle with me for a few months to do some load development on.
I've read a lot of fantastic optics comparisons on this site by guys with a lot of experience...I'm not that guy, and this isn't that high quality review, so if you're after resolution charts and through the scope pics, you'd probably be better off stopping now and clicking on the next thread.
What I am is a who has always tried to balance price vs. performance - always looking to spend what I must in order to maximize MY ability, without spending too much on 'niceties' and limiting training, or too little on something that was going to fail me. What I've ended up with are a bunch of $750 - 1,500 optics over the years. * I should note here that I buy on closeout (I'm cheap), so that figure would rise to $1,000 - $2,000 at introduction. I've never lost an animal due to a glass or mechanical issue, and in my wheelhouse of shooting (100 - 750 yards) I am *rarely* fighting a quality issue that fatigues my eye prematurely...the exception being a Bushnell DMR II that has a lot of CA to my eye.
Enter the S&B 5-25x56 that my buddy has. I know that some probably don't consider this old warhorse to be 'tier 1' or 'alpha glass' anymore, but anything over that $3K mark is tier 1 priced in my book. His is a relatively recent manufacture.
My most expensive day optic is the XTR Pro on the AT-X in the photo. I do own two thermals, so I've spent money before. But I digress in that I spent well under normal retail on the Pro.
I've now put probably ~3-4 hours total time with these optics next to each other in all of the possible conditions that I might come across (notice the wet patio in the photo as it was misting and foggy that day with about 400 yards of total visibility).
So for the layman like myself who wonders if that extra $2K is going to net him or her twice the shooting experience, I'll just state now that it will not. Actually the diminishing returns are pretty apparent here...but there absolutely is a quality difference. I own Wilson Combat, Ed Brown, Les Baer, Dan Wesson, Colt Custom Shop etc... 1911s, and I can tell you that all 1911s are not the same - even though they all shoot just about the same. In fact, one company's flagship can be well ahead of another...even though they are priced similarly.
In broad daylight, the XTR Pro and S&B are really close in that subjective "glass quality" category. Really, my XTR III (US made) isn't but a couple percent behind. Putting all optics together and looking at trees at ~200 yards there was no leaf that the S&B could make out that the Pro couldn't. FOV at 25x though goes to the S&B, but it isn't by a lot. If I had to assign an arbitrary number to the S&B it would be 95, and the Pro would then get a 93. There is a tad more color "pop" to the S&B, and a tad more hue to the Pro. Light mirage saw no difference, but I did not get to use both under heavy mirage yet. Shooting paper or steel or animals would see no optic holding an edge that would be noteworthy.
In the fog and mist the S&B crept out, but by maybe another point (95 to 92 we'll say for argument's sake). Looking at our Angus cattle at 140 yards on 25x I could still make out the same black flies clinging to the black hair. I could see the same hair pattern on the faces, and identify the same small tufts coming off the tails. Maybe though the Pro was just starting to exhibit a hint of CA with the light and fog. The S&B had zero. At 385 yards (the extent of that angle and conditions) I could still see my blue t-post target stand with both scopes though. Again, you weren't going to lose anything on paper, steel or game with the Pro compared to the S&B.
At dusk there is maybe one more separation point again (95 to 91). This time I was on 15x (or at least as close an approximation as the ring stated). Shadows in the trees that you couldn't see into with the naked eye had foliage details stand out well with both optics. Each provided extra minutes of shooting light over the naked eye, even at 15x. Maybe, just maybe you might get an extra minute or two with the S&B...but it is impossible to accurately say as light is fading as I'm switching back and forth on my belly between rifles. Is there a difference? Yes. The S&B is better, but to put it into perspective - $2K for ~ 3-4 total extra minutes of hunting (not that either is a hunting optic).
Turrets on the S&B are noticeably more tactile and audible. Not that the Pro is bad at all, but there is a more noticeable difference here than with glass quality. Plus the S&B has both the tactile pins as well as windows to show you which revolution you are on - which is where that extra money starts to really go into IMO. There is a touch less play in the S&B turrets too and they lock. The Pro also has much more of a wind-hold windage turret in that there is a lot less real estate to grab onto and adjust with. I hold wind anyway, so that isn't an issue for me. Guys that dial wind might find the Pro less enticing. We aren't going to compare a lot of features here though, so I'll stop there.
*Both scopes have been repeatable and mechanically accurate in to the limited extent of my use.
* Neither scope has been abused, so I have no comments as to durability under extreme events. The S&B has a great reputation, and I have several old Burris XTR IIs that have seen hundreds of miles bumping around the ranch in a SxS without even the slightest zero shift...I have zero doubts that either the S&B or Pro would fail under normal and continuous use.
* QC and Warrany: Well, there are several recent gripes about the Pro. Not much about the S&B over the couple of decades that I've known about them. This is untested though between my two examples (and I hope it stays that way).
Bottom line: Is there a quality difference? Absolutely. For guys that run alpha glass, the thought of downgrading to something like a Pro or equivalent $2K scope is off-putting, and I get it. After my first Wilson Combat, I stopped buying production 1911s. Saving up for another few months to a year was worth it to have that feeling of a quality semi-custom pistol...even if you can't tell the difference between a 1" or 2" pistol at 25 yards.
For guys that run mid-level optics and wonder if they're leaving something on the table though - I wouldn't stress it as long as you've proven that your current scope tracks true. If you're so competitive as to need that couple of percent difference that I noticed with a $3K+ optic... chances are that you've spent 3x the amount of a alpha scope on matches this year anyway.