Eye relief.
Really, that's it.
The Zeiss Victory has juuuust a smidge more eye relief than Leica and Swaro. I think it's only like 2mm but it's a big difference. At the time I bought my Leica 10x42 Ultravid HD's, they barely worked when I was wearing my glasses. That's with the cups twisted down. On the Zeiss, well, they were simply so much more forgiving with the eye relief. That extra 2mm meant I could keep them off the lenses of my glasses. It's funny, I had read about the eye relief difference but what I was actually looking for at the time was the lightest 8x32 I could get and the Zeiss won by maybe an ounce. The secondary effect was discovering the eye relief part.
Now, yes, you can of course adjust the Bins to work without glasses but that was a PITA. My eyes were bad - as in, can't see beyond maybe 6 inches to read. I was so near sighted I could read the words in a bank check signature line unaided (*it's not a line, btw...) Forget watching the TV, just blurs and colored blobs. I've worn glasses since I was 6 years old.
Anyway, the Leica's are ever so slightly sharper, the coatings are designed to enhance contrast and they work better in low light not by being brighter but by adding contrast to the color in the animal spectrum (i.e.: what an animal looks like in the shadows). The Zeiss are brighter, have better color but aren't quite as razor sharp (It's brutally close...were talking like a 9.8 vs 9.5 out of 10 here) and don't have the edge in contrast.
BUT, the Zeiss have eye relief. In practical hunting, not having to take off sunglasses or glasses when hunting (*Particularly in broad daylight Africa) the Zeiss have a real, practical edge.