I've had both, and like both very much ... they are simply different from each other ... not "better" or "worse" ...
Glass: Zeiss generally has slightly better image quality (only slightly)
Reticle: Zeiss reticles are etched glass, and their reticle designs are (in my opinion) superior to Leupold's, especially comparing the standard duplex versions from each mfg.
Weight: Zeiss is usually a couple (maybe 3) ounces heavier when comparing similar power ranged scopes
Eye Relief and Eye Box: Leupold wins, hands down ... but then again, it's pretty much that way when comparing a Leupold to ANY other brand scope
Overall Scope Design: Zeiss has a larger ocular with the fast focus eye piece ... some like that, some don't ... it can get in the way when mounting your scope very low (due to bolt handle clearance issues, especially if you use Butler Creek caps). The Leupold, on the other hand, can be mounted a bit lower with no worries about bolt handle clearance ... very important to most people that have rifles/stocks that fit them well, and require that the scope be mounted low for proper eye positioning
Aesthetics: Of course this is purely subjective, but generally the Leupold scopes seem to be more "sleek" in design ... As stated above, the Leupold scopes weigh less, but they look/appear to be MUCH smaller and lighter, which makes a big difference to many when they are concerned with how the scope looks on the rifle ... I have to admit, I prefer the look of the Leupold over the Zeiss, even though I think the Zeiss are handsome scopes ...
Accessories: Leupold has a few different styles of target knobs you can have installed ... Zeiss only has one style ... Leupold has sunshades, and even has their own line of "designer" caps for the lenses (some that flip up, and some that just screw on and off) ... Zeiss says they are planning on releasing some sunshades for their conquest line, but has not done so yet (they say they are still working on producing them, and they should be out this year) ... Both mfg's will let you send the scope in for parallax adjustments, and for reticle changes, so that's an even deal in comparsion ...
Bottom line, is that you're not gonna be upset with either ... both scopes have lifetime warranties, and are very good with their customer service. Best to get to a store with both, and persuade them to let you walk outside with a few of each and really compare them in low light ... decide which is best for you, and don't look back ...
