I own a Swarovski 20x60 x65mm. spotting scope. I bought the 65mm. because the overall size of the 80mm. was much larger. After I compared the two head to head my choice was an easy one. The quality of glass in the standard model verses the HD??? I honestly could not tell the difference in quality.
I also compared the Swarovski, Leica & Zeiss head to head, before I bought my Swarovski. I picked the Swarovski because I like the adjustments better on it then the Leica. The overall size of the Zeiss was larger than the Swarovski. Iprefered the 45-degree angle on the Swarovski eyepiece also.
If you get the 45-degree angled eyepiece, it will rotate so you can adjust it for a better fit, if you use a window mount? The 45-degree eyepiece is also nice if you are sheep/mountain goathunting. You can set your spotting scope up on a small tri-pod & glass for sheep/goats while you lay flat on the ground. As a person that has sheep hunted, I can tell you this is a real added bonus.
I bought my spotting scope 5-years ago. The cost of optics has gone up every year since then. I know I madea good purchase back then. My spotting scope will last me a lifetime.

Best of luck,

WK