I would not do that if I were you.
Unless you have a photo taken from a 65 mm and an 85 mm at the same time, under the same conditions, at the same distance, you won't get an accurate comparison.
One guy might post a fantastic photo from a 65 mm scope and another guy might post a poor image from a 85 mm scope.
The bottom line is, you cant get an accurate comparison this way.
You can try to understand the concept and make an educated decision.
Your scope, WITHOUT the eyepiece has a "focal length". Not 100% sure on the vortex, but probably around 400 - 450 mm.
Then, the zoom eyepiece, further magnifies this image.
Magnification is measured not by how many times the image is magnified, but by how many times closer to you the image appears to be.
That way, 10X is the same on one scope as it is on another, regardless of the initial focal length.
But, a scope with a lower focal length, will need more magnification than one with a higher focal length.
A classic example of this is the new SWAROVSKI ATX and STX series scopes.
The 65mm, 85mm, and 95mm all share the same ocular module, but the 95mm has a higher zoom range due to a higher focal length on the 95mm lens.
This means that you get 30X magnification on the same setting as 25X with the 85 and 65mm lenses.
So, you will get the same level of quality but at a higher power.
Due to focal length.
So, look into vortex. See if the focal length is smaller on the 65 vs the 85.
If it is, realize that under the same conditions, your results will be better with the longer focal length, at the same magnification.
If they are the same, focal length is not an issue for you.
Then, consider that you have light transmission and try to understand how light is effected by magnification.
The 85mm scope is going to let in more light at higher magnification.
This matters because when digiscoping, the camera settings that sense light will need to be adjusted based on how much light is getting in.
No matter what, you will get more light through to the camera at 85mm than you will at 65mm on the same magnification.
Under optimal conditions, the 65mm scope can take great images, the 85mm will have a better "range" of usable light conditions, dawn and dusk will see a difference.
Under poor conditions, such as low light, heat waves, cold waves, haze, or looking into the sun, it won't matter much, because quality is going to be poor with both.
For taking photos, the 85mm is the way to go.
It may not be the way you want to go, price wise, or size and weight wise, but it is the way to go for getting thee most out of digiscoping.
You may also get a 65mm and find that you get fine images that way. But it will be easier with the 85mm.
Its not about opinions or comparisons, it just about understanding the concepts involved.
There is a reason why an 800mm camera lens has a large objective diameter.
Its because an 800mm lens with a smaller front end has too much magnification and not enough light.
The concept is the same, just a bigger problem.
You can buy a cheap 400mm lens with a 3 inch front end, for $1,300.00 but the same 400mm lens with a 5 inch front end will cost you $4,000.00
Because it will get better results.
Same basic concept.
Hopefully this helps you understand what you are trying to do.