Did a little deer hunting up in the Panhandle of Texas this past weekend. Three of us took quite a few premium binocs to test side by side at dusk and dawn. Typically viewing pasture and brushy areas. We also scanned closely into the evening sun to test glare.
Swarovski EL SV's (10X42); latest generation
Zeiss Victory FL (10X42)
Leica (12X50 Ultravids; Non HD)
Swarovski (SLC 10X42 1st generation).

I reality the first three all had about 4MM exit pupils and performed equally. We could not tell ANY difference between them. We are speaking in the realm way prior to dawn when no color existed; Just gray scales. With any of these you can make out game far prior to being able with the human eye. Our tests were conducted at 135, 200 & 500 yards
The first generation Swarovsky SLC's were not quite as sharp in this test but to be fair, they are probably 20 years old. They are still brilliant in normal daylight.
All did a great job looking into or close to the setting sun.
What surprised us most is we tested a Leupold Gold Ring HD spotting scope (Flourite objective; 60MM. At 15 power (4mm exit pupil) it was as good or perhaps a bit better in the twilight as the premium euo binocs. It did not do as well looking into the evening sun. We did experience some glare.
So, take your pick of the euro stuff. In the real world (hunting) there is not a lot of difference.
IMHO; I would pick Leica's as I believe they are the most durable. That being said i sure would like to try out a set of the new Zeiss Victory HT's. Wish I had a pair for the test..

EZ

Thanks for the report - most interesting. The exit pupils can be calculated to be 4mm-plus, of course (giving adequate twilight values in binoculars, if not riflescopes), so any differences would be mainly in glass and coating quality.

If exit pupils are equal, lens quality and light transmission is equal, and the instruments are properly focused, then the greater the magnification the better the low light resolution. This is because of a simple fact: If it is bigger, it is easier to see!

I've found that with the typical 3-9X40 hunting scope of decent quality the best low-light resolution comes at around 6-7X. If your eyes are older or you've been a life-long smoker, either of which tends to restrict your maximum pupil dilation, then you might find better low-light resolution at maximum power since your scope will still provide an exit pupil as large as your eye can use. Young, healthy eyes might do best at 5-6X; but it always depends on striking the right balance between having a sufficient exit pupil (brighter picture) and more magnification (larger picture).