I will say, having 3 zeiss conquest scopes of various lines, and 4 Leupies, the Zeiss glass is just a smidge clearer, by just a tad. And I have bad eyes, so I tend to notice the details like eye relief, etc.
If I had my druthers, dollar for dollar, I'd own more Zeiss. But the Leupold warranty is better, and I promise you, dealing with a German company with regards to warranty issues will never be as good as Leupold. German companies are more of the "materials and workmanship, and we mean that" companies. In other words, don't sent them an abused scope, even if it was an accident, and expect diddly.....
OTOH, as it is said, better to have a product that has a poor warranty and performs flawlessly than a product with a great warranty that never works quite right..... Just that there are lots of satisfied Leupy users out there too....