Out of curiosity is there a clear winner for the award of best glass? I know it's subjective and splitting hairs in some cases... But taking into account CA, resolution, light transmission, tunneling....
Is there a brand or even a couple of brands that really stand out above the rest no matter who's looking through them?
These types of posts are always very difficult because you're asking us to give an objective answer to a subjective question. First, you need to define what does "best glass" mean to you? There are many elements that go into an optical formula when designing a scope, but there is something that no single manufacturer can account for and that is the differences in the human eye and our own personal preferences - the things we like. So asking a question like "who has the best glass" is almost akin to asking "who makes the best ice cream", we all have different tastes and while you may find a group who all love Chocolate you'll just as easily find another group who prefers Vanilla and then among the Vanilla makers, is it brand X or brand Y or... The same goes for scope manufacturers and the different scopes they make, just because Vortex makes the AMG (which has great glass) doesn't mean their Diamondback is going to have the same quality. In general, within the optics community, you get what you pay for, so the "better" glass typically comes in the higher priced optics.
In the not too distant past, the general consensus was that the scopes with the best optical quality came from German/Austrian/European descent; however, over the past few years the introduction of high end Japanese glass and designs has put a dent in that trophy; hence the responses above where many list out Vortex Razor Gen II's, or Nightforce ATACR F1's, etc. who are all using Japanese glass.
But to get back to the OP's question, there is no "award" for best glass and, in fact, there is no spec that is provided by any manufacturer that determines how good their glass is, it takes some pretty expensive equipment to measure resolution in lpm (lines per millimeter) or the like, but resolution is not definitive in and of itself, there are other qualities like color, contrast, flare, CA and more that go into a great optical design and this is where a lot of personal preference goes into the mix. For example, my eyes tend to prefer a "warmer" or yellower color cast to the image vs. a "colder" or bluer color cast, my eyes can also pick out CA pretty quickly and while it is an annoyance for me, it does not bother other people at all. Then there's terms like clarity, pop, eyebox, parallax/depth and so forth that can further confuse matters.
In the end, you have to define what is the objective for you, so when you ask who has the best glass or the like, what are you really looking for? Are you a competition shooter who is looking for the edge in being able to spot the gray steel target that's blending in with the background at 768 yards? Or are you a hunter who's looking for a scope that will help them identify whether or not that bull elk is legal 30 minutes after sunset when it's hard to see how many tines are sticking up, or is that a buck in the thicket or a branch? The good news is, many of the top tier scopes excel in these areas so you no longer have to decide on one scope for one thing and another for something else (we'll table the SFP vs FFP arguments for now).
So while Schmidt & Bender, Zeiss/Hensoldt, Swarovski and the like may have ruled this market not long ago, the likes of Vortex, Nightforce, March and others have steadily encroached upon their territory and the likes of Tangent Theta and Minox ZP5 may have actually exceeded in some areas. What might be drawing even more attention these days than "good glass" are good reticles and that's where you'll start seeing some interesting trends, Kahles has made some great strides since their Gen III scopes teamed up with Shannon Kay to create the vaunted SKMR (Shannon Kay Milling Reticle) reticles. But here's the problem with trying to define the "best", let's say I recommend the Kahles, but if you're one who is really bothered by CA I'd tell you to steer clear of the K624i, so maybe I recommend the Minox ZP5 with MR4 reticle but you're a turret purest and are bothered by minute amounts of play between clicks, so then I'd steer you towards a Tangent Theta but you insist you must have a .2 mil reticle and so I recommend the new Nightforce with Mil-C reticle but you tell me the scope has to be less than 30oz so now I recommend the Vortex AMG 6-24x50, but you insist you must have lower than 6x magnification so now I tell you about the March 3-24x52 and... the list goes on, and on, and on.
Again, this is why it is so very difficult to quantify who has the best glass or best scope because there are so many other factors at play, so a better question is to ask, "who has the best scope/glass for me and my style of shooting" that is something we can narrow in on by defining what kind of shooting you do and what are some of the constraints that you want to keep within, constraints like weight, cost, length, mechanics, forgiving or easy eyebox, forgiving parallax, etc. and then realize that even with all the constraints you're still going to get multiple choice answers and in the end you will have to choose for yourself and be content with your choice unless something serious is wrong with you scope, which at the alpha class prices you will find few and far between. All too often we ditch a tried and true scope for another over petty things, things like trying to find the absolute best glass when you've been perfectly happy with your Nightforce for years now; can you find a scope with better glass, arguably yes, but what have you gained in doing so?
My recommendation for anyone looking to upgrade your scope to something more expensive is to ask yourself why? Does your current scope no longer serve your needs effectively? If you can answer with an emphatic yes then maybe it is time to upgrade, but if your current scope gets the job done and done well, again I have to ask then what is the real reason you want to upgrade? Right now I'm sitting here looking at a bunch of scopes for my next review, but the real question is, do any of them offer me anything more than the scopes that currently sit on my rifles, I could argue that yes, a Schmidt 3-20 gives me more bottom end than my AMG 6-24 or the Leupold Mark 5 3.6-18x44 is a lot shorter than the Burris XTR II 4-20 and so forth, but all are fantastic scopes in their own right. The great news is that here we are in 2018 and there are so many great tools to choose from and no longer do you have to pay $3k to get a great tool.
