Swaro Eyepiece recommendation?

[BlacktailStalker]

Your 60 will be useful at closer ranges where you can count rings... if you need to.

[Jagermeister]

There are exactly the same number of elements (9) in either eyepiece.
Spherical lens cannot converge parallel light rays at a single focal point completely and this distortion is more pronounced in wide angle lenses. It takes a greater degree of grinding and polishing of one lens to correct the distorted image in WA lenses. This lens is called an aspherical lens and they exist in most all quality scopes. The cost of correcting is greater for the wider angle is greater.
Mirage is not an aberration of an increase in power. Mirage is a phenonemon of optical illusion created as light rays bend (refraction) as they pass from a cold air into warm air.
Low light is known as the twilight factor and twilight factor is.......

A number used to compare the effectiveness of binoculars or spotting scopes used in low light. The twilight factor is found by multiplying the size of the objective lens (in mm) by the magnification and then finding the square root of that result. The larger the twilight factor, the more detail you can see in low light. A twilight factor of 17 or better if usually required for reasonable low light use.

The twilight factors for the STM/ATM 65 using the 20-60X are 36-62 and for the 25-50X are 40-56.5. In the STM/ATM 80 the t/f numbers are 40-69 using the 20-60X and 44-63 using 25-50X. Nothing really outstanding IMO. If you are considering of becoming a professional birding photographer looking for the super duper bird of paradise shot, then buy the 25-50X. If not, save the $200+ difference and stick with the 20-60X at the lower cost.
That's my 2¢.

[knockturnal]

I have the ATM 80mm with the 25-50wa and love it. If you are around kelowna and want to check it out to compare to another, I'd be more then happy to show it.