I've had a pair of the 12x50 Leica Ultravids for the past 18 months now. Prior to getting them I did consider the 12x56 Zeiss Victory II model. The primary reason why I choose the Leica over the Zeiss was because they were 8 ounces lighter in weight.
Aside from the weight difference the Leica's have other very nice features. First, they are fully waterproof. Second, they're fairly small for their aperture size and pack very well. Third, they can close focus to 10.5 feet. Fourth, they have excellent ergonomics and are comfortable to hold (in so far as a it is possible to comfortably hand hold a 12x binocular). Fifth, you can set and lock the diopter adjustments for both eyes rather than just for the right eye. Sixth, if you want to occasionally use them with a mount, Leica has a great tripod adapter that works with them. Seventh, they come with a very nice, perfectly sized, condura case. Eigth, they're small/light enough that you can and get good views (although, it is best to be seated or leaning against something when using them), but the magnification is also high enough that they can give you great views when you mount them on either a monopod or tripod. Ninth, they have a huge field of view - 5.73 degrees true and 69 degrees apparent. Tenth, their optics are superb and retain their sharpness across most of the field which is rather impressive for such a wide field binoculars. Also, they're very bright for such a high power binocular.
On the downside,their focuser wheel is not as smooth as I'd like (but it isn't terrible either) and their price is very high.
Another very nice 12x binocular is the Nikon 12 x 50 SEs. They're a porro prism design and are not waterproof. They have excellent ergonomics and superb optics and they sell for about half the price of the Leicas. They have a 5.00 degree true field and a 60 degree apparent field and have very good edge sharpess for a binocular. They're also very light - only 31.6 ounces. I used to have a pair and liked them, but I switched to the Leicas because they were both waterproof and more compact so they're easier to take along on a hikes or an overnight backpacks. The other reason I decided to get them rather than keep the Nikons was because of their huge field of view.
John Finnan