Having recently gone through the process, you might find this of interest:
Sliding over from the Bino subgroup. I know next to nothing about scopes. Been informally birding for a very long time and happy with my grab and go system of binos and Fanny pack. Have gotten a bit more focused last couple migrations. Reluctantly admitting the desire to see stuff further out...
www.birdforum.net
I am admittedly, still a rank amateur re scopes, with very limited experience. I am though very happy with this purchase and the utility a scope has added to birding where I do, often in open, over water places.
In fact Im shocked by how useful it is!
So far I find the variable X quite useful. It was a feature I never used with riflescopes, but find I use it often on these, using lower X to get on the bird, then turning to higher to see details... I cant imagine one fixed eyepiece X that'll allow that utility where I bird, given the variable distances from my vantage point. Maybe the point is if one birds mostly in the same places, a nice working compromise of a single X works fine. As we bird among several venues, so far I appreciate the variable X.
I alluded to a spread sheet I made down in among those posts, just above my final. Like a lot of written specs that static, data oriented approach only goes so far. The Opticorn MM4 60 vs 77 is a case in point.
Looking at the array of 4 scopes this dealer was kind enough to set up, the size (and weight) of the 60, compared with the 77, the other 2, (Swaro 65 regrettably not available), the 60's weight/size advantage shrunk almost to irrelevance. Once you step back and consider the task that is coming - that is carrying the blasted combination of scope plus tripod around, how you carry, how you set it up, become aware theres now a thing you have to think about to avoid knocking it over, how quickly you get on the target seemed and still seems the more important consideration. The relative size and a few ounces of weight of just the scope seems not so important. I voted for the optical benefits of the larger objective.