Im going to relate a true story, you can choose to believe or not as you wish.
Happened on Friday of the second week of the Pa buck season about 15 years ago.
There were four of us staying at our camp, and three staying at another belonging to friends.
All well experienced at hunting long range, and all having good large glasses.
We chose to hunt 2 separate locations looking across the same valley about a half mile apart.
4 of us at one spot and 3 at the other and staying in touch via walky talkeys.
Weather conditions could best be described as typical gloomy and dark as is common in Pa.
One guy had recently sold his twin 77 mm Kowa spotters in favor of twin 80 mm Swarovskis.
Another guy was using 80 mm Kowa Highlanders, and as a mater of fact was also a Kowa rep.
I was using a set of Oberwerk 100 mm binoculars with both 25x and 40x eyepieces on turrets.
Another guy was also using a set of those same glasses. The others were all using twin 60 mm Bushnell Spacemasters. So there were 2 sets of 100 mm glasses, 2 sets of 80 mm, and 3 sets having 60 mm.
About 2 hours into the glassing our group had seen nothing. After a radio check we found the other group had a buck laying down looking right straight at them at about 900 yards. PRoblem was that due to the conditions they couldnt tell if it had brow points. They knew it had decent size horns with a nice Y on both sides, but couldnt see brow points to determine it had al least 3 points on at least one side which would make it legal.
An hour later they still didnt know, and that was all my late buddy Ritch could take. He said to his son get me to hell over there, and ill put points on that thing with my Swarovskis. When we arrived there one guy was busy building a fire for cooking lunch, and he said to Rich there it is buddy have at it. Ritch said if i cant put points on that with my glasses ill kiss your arse. Well its a good thing he wasent held to that because an hour later with now 7 sets of good glasses we still didnt know.
But there became a second problem, in that within about 50 feet there was yet another nice buck laying that we couldnt tell was legal either.
After another hour or so for some reason the conditions improved slightly. Which was enough for everybody even with the 60 mm optics to see it had brow points. We did end up killing that buck which was a 7 point eastern count. We had assigned a guy to watch the second one while we were shooting at the first one.
But then decided to be happy with getting one of them.
So there you go, proof that conditions and not always optic size and quality is what makes the difference.