Looking in dark shadows 75 yards away and looking into the desert during the day is the best way to test the extremes. I've been a high end glass user for 23 years. I own high end Leica photography equipment, Swarovski binos, spotting scope, rifle scopes, and Zeiss rifle scopes. For light gathering and no glare, I haven't seen anything that compares to the Swarovski. That does not mean there isn't any, I just haven't found it yet. I am not partial to any brand, I compare performance.
For color rendering, Leica is best. That is why bird watchers and photographers chose Leica.
Zeiss is very bright, but often too bright with glare.
Ideally, we would be able to borrow all three scopes to compare, but the retailers won't let us. So set them up in the store and start looking into the darkest corners in the ceiling, you will see differences in the scopes. My first Swarovski purchase in 1985 was a 1.5 to 6 x 42 w 30mm tube. The salesman and I went outside and I looked through the darkened doorways of other businesses to compare the light gathering of the scopes. I could see details on the walls in the shadows through Swarovski where the other scopes just showed black shadows. You don't need to take them out to the forest to compare.
