I have owned the Zeiss 10X45 w/ Rangefinder, The new Leica Geovid 10X42 Rangefinder and the Swarovski 10X42 EL Rangefinder.
All three are amazing glass to look through, the Zeiss a little brighter do to being 10X45. Swarovski and the Leica are awesome as well if you lined all three up and looked through them all side by side I would hard pressed to tell you the difference between the glass
The Swarovski and Leica ergonomics are great, they fit in the hand well and are extremely comfortable to hold. The Zeiss are bigger fit me well but just big.
The Range button on the Zeiss and Leica are on the right side of the binocular frame which makes it easier to find and press, however I have good size hand and have no issues with the Swarovski. If a person has small hands this could be an issue
The Zeiss and the Swarovski rangefinder are one push of the button and you have the yardage to the target, they both are very fast in getting you the yard and accurate. The Leica I had to press the button twice to get a range just like I do on my Leica CRF 1000
The Leica and the Swarovski both have angle compensation with that said the Swarovski the angle compensation starts after 33 yards. The Leica if I remmeber correctly was 10 yards (better for bow hunting) The Zeiss will only give you hold over (no built in angle compensation)
The Leica will give you the Temp, Barometric Pressure, Ballistic Processor and some other stuff I can't remember its a lot more information than the Zeiss and the Swarovski will give you
If you are big into long range shooting or rifle hunt then the Leica or the Zeiss would be a great choice. For me I bow hunt so the Swarovski are what I use now. I sold the Zeiss and I took the Leica's back because I was having so many issues with the rangefinder, I could never get a consistent range on a target. I would range a car and get 4 different readings
If the I didn't have so many issues with the rangefinder I would have kept the Leica; I took them back to Cabela's and exchanged them for the Swarovski's and have not been disappointed
That's just my two cents.