I don't have any info but apparently zeiss hired the guy who designed the geovids to make their units. of the big 3 leica has the most RF technology to pull from because of their relationship with vectronix and other RF products out there.
each of the big 3 have their own advantages. I might have bought the zeiss at one point but for me the eye relief was a tad short. They also seem pretty blockish in the hand. The newest leicas don't work for me for a couple reasons the most puzzeling is it appears they have more green tint than even the model they replaced, they also are not as crisp on the edges as the model they replaced. currently using swaro EL range, I like everything about them I just wish instead of a circle they had a crisp box aiming point like leica uses. but then again that might change the way they are focused because both barrels are used for the display. The focus function of the swaros is the best of any binocular I have ever used. so the fuzzier circle that is sometimes difficult to pick up in different lights may just be a by product of that.
