I've owned leupolds from vari-x to mark 4's. Mostly use vx-2 and 3's. I've owned zeiss conquest in 3 different magnifications. You can't go wrong with either. They are both 1" tubes, both have good eye relief, both have good warranties, but I have found leupolds warranty, customer service, and custom shop to be one of the best of any company I've ever dealt with. But I hear good things about zeiss USA also, just no personal experience.
I like zeiss's zoom ring and eyepiece adjustment better. I like leupolds tube construction better. Zeiss appears a little clunkier, leupold a little sleeker.
Zeiss coatings give a little bit of blue/green tint when I look through them that I don't care for much. If you compare the conquest to the newest vx2's you'd have a pretty fair and equal comparison. The vx3's would probably test a little better on technical resolution tests, but I doubt most people could see the difference on a big game scope (3-9x40 or thereabouts).
I use leupolds. I can get a leupold scope in more configurations, at more different price points.