MudderChuck

A lot of it has to do with the coatings/filters. Sure the grind of the optics counts, but for my use, the coatings are more important. My eyes aren't all that good anyway, so clarity isn't nearly as important as usable light gathering.

I have a pair of (way old) Nikons, they have a fairly robust UV coating on the lens. In low light, a lot of what you see is reflected light, mostly UV (or near UV). Or objects that absorb UV (or near UV), you see a black nonrefective shape like Hogs. I call Hogs black holes, everything around them reflects a little, but true Boar don't reflect much light. The robust UV coating degrades some frequencies of low light. This may be more of a subjective than objective statement. What works for me may not work for you, in subtle sorts of ways.

My Nikons work OK in the daylight, I see much less with them at night or low light than I do with my Optolyth. I'm far from an expert, but did notice that the Nikons had a blue coating, wavelength unknown and my Optolyths have kind of a red or rust colored coating. On most of the optics the coatings are patented.

Both manufacturers are unlikely to sell you a pair of glasses that will burn out your retina, but do filter differently. One, the Optolyth, definitely works better in low light.

I got a heck of a deal on the Optolyth and they are comparable to the Swarovsky. I got a promotional deal for the Optolyth when they first started expanding into the U.S. market. Definitely a better optic, close to the best, whether they are worth the full price is anybodies guess and likely just opinion anyway.

Best advice, try them out extensively before you buy. The salespeople may or may not be open to you running outside with their wares, daylight and night time. I'd shop until I found a retailer that will allow you to test them. A relatively large ticket item, that is designed to last decades, is not a choice you want to make on the spur of the moment.

IMO every bodies eyes are little different and what works for me might not work as well for you. Again we are back to the coatings. I prefer a bino that lets in as much UV light as practical and safe.