Hi Conor,
I've had both the Zeiss Diascope 85mm and the Swaro ATS 80 and had the opportunity to use my friend's Leica Televid 82 over the last 8-10months. Basically the only optic store in my town was selling stock that had sat around for about a year so offered some good discounts on all three scopes. I bought the Diascope and Swaro and he bought the Leica a couple of days later.
My perception on the quality of the image aside, the other key driver that influenced my choice was also my own experience and forum feedback on warranty support from all three brands in Australia.
From that perspective, Swaro won hands down. All my other optics (binoculars) are Swarovski and I have only great things to say about them in the dealings i've had so i was naturally drawn to the ATS 80.
Now to the image....
The Zeiss appealed because of the "larger" diameter and the 20-75x zoom. Optically is almost no noticeable loss in brightness on the image at full zoom. In terms of the view, FOV isn't as wide throughout the range as on the Swaro (25-50x eyepiece) and the Leica (25-50x eyepiece) and it narrowed considerably through the mid range.
Image on the Zeiss was extremely sharp in the middle but soften considerably at the edges in the last 10-15% of the field. This scope also had the most CA (relatively speaking) at edge of field. Finally, eye placement was the easiest on this scope - no blacking out or kidney beaning and at 20x with an 85mm objective, exit pupil was the most generous.
I had no issues with the unique dual speed focuser and as i tend to view on-axis, the superb view in the centre more than made up for the soft edges.
Onto the Swaro - I'll state upfront that I found the Swaro's image to be the best. It has a big FOV with a very bright, sharp image. Field was flat from edge to edge and CA was hardly noticeable. I found colours to be a bit more natural compared to the Zeiss (the Zeiss to me had a slightly bluish tinge comparatively - it was only apparent when using both scopes side by side)
Obviously zoom range wasn't as wide but the scope itself was significantly lighter and more elegant. I found eye placement on the Swaro to be the trickiest. I still do - i have some days where I can observe for several hrs with no issues and other days where the scope just frustrates me and i'll constantly be twisting the eye cup to try and get better eye positioning. When I bought it, i thought I could "train" myself on eye placement - that challenge continues.
With respect to the Leica, this brand has always been a bit of an unknown to me - i have never used or experienced Leica products and I have no idea about their warranty. I've just picked up on a number of local forums that they are difficult to deal with in Australia so this had already made me cautious. I found the view through the Leica very similar to the Swaro - it was a bright clean image with a wide FOV - possibly a little wider than the Swaro at 25x. I thought it lacked the contrast that the Swaro had but again only found this when using both scopes side by side and swapping frequently. Eye placement was easy.
Already being hesitant based on customer service feedback, the clincher for me to disregard this scope was the tactile feel of the focus wheel (on the Leica they are half embedded into the scope body). When I turned the wheels (both the fast and slow wheels) they felt like the motion was dampened with a slight "springback" i.e. I would finish focusing the wheel and as I eased off and rested my finger, i felt it "roll" back the other way by 1-2mm.. Its an odd one to describe - it just didnt have the crispness and precision I had felt in both the helical focuser of the Swaro or the focuser on the Zeiss.
so based on this, I picked up the Swaro and the Zeiss.
My mate looked through the Leica and agreed with my opinion of the focus wheel but equally, enjoyed the view. He managed to get a slightly higher discount by bargaining with store and bringing up the focuser (which the store assured him was working as designed) and subsequently ended up buying the scope.
Since then I regularly had the opportunity to look through all three (as has he) and we're both comfortable with our choices. He still has and enjoys the Leica. I love my Swaro but the eyepiece can be a pain (placement wise - eye relief is great).
More recently the Zeiss didnt get used as often because it was a much bigger/heavier scope and I stopped taking two scopes out, particularly when bushwalking. So I recently sold the Diascope body and intended to keep the eyepiece for use in my 11" telescope, however I've now sold that telescope as well so the eyepiece is also on the market.
Regarding the Swaro, I'm now looking for a good condition 30x SW eyepiece to compliment the zoom so that should keep me happy with respect to eye placement etc.
I've thought about looking at Kowa but again, the customer service in Australia is an unknown to me and I'm cautious about the eyepiece which still has reported issues with the internal anodising flaking off and settling on the internal lenses..
I do want a second scope for my wife so i'm considering the Swaro ATS 65 now - it should go with the 30x eyepiece perfectly and make a great travel scope.
cheers
Jeelan