I guess it depends on how you are going to use it?
From the truck or an atv, the 80mm is going to pull more low light and weight won't be an issue. If packing it around on your back, the lighter 65mm would be the way to go.
I like angled if it has a rotating collar. I can use it from a truck window by rotating the scope. Looking up hill I can use a shorter tripod, weighs less too, and don't have to worry about neck strain. Downhill if needed rotate it. It is a little harder to find the target but you get better at it after a while.
