My preferences are:
Straight for window mount. Straight for shooting, as spotter seated or standing, especially varying target distances.
Angled for spotting from prone (assuming that you can rotate the scope body to allow the shooter to simply switch from riflescope to spotter). Angled for use by different people of various builds and stature, especially standing but the scope body needs to rotate. Angled for long periods of glassing.
I recently sold my last straight scope and went out of my way to buy an angled scope (three actually).
I just spent a week on my first backpack mule deer hunt. It was pretty big country, with fairly big mountains and pretty deep drainages (i.e. looking way up, and way down). I used an angled scope and binoculars on my tripod. My buddy had a straight scope. It was a good opportunity to see if my opinions would change. I normally hunt from a basecamp and view out to moderate ranges. And also do a fair amount of target shooting in the field on the Oregon coast with extremely steep angles.
I still like both, angled and straight. As some others previously mentioned, going from binoculars on the tripod to angled spotting scope is not ideal. So in the heat of the moment, when an animal was located, it took extra time to get back on it with the scope to confirm if it was worth pursuing. Straight scope being quicker.
Also, as Stick mentioned, I have preferred a straight scope when hunting or shooting on the Oregon coast. The ocular is less likely to collect water and can stay surprisingly dry without much effort with the light rain and mist.
I did have the opportunity to observe out to two miles and beyond on this hunt. At those distances, my 8x binoculars were not of much use. At least for deer, but I could certainly spot goats with their white coats on occasion. So it wasn't like I was switching from tripod mounted binoculars to spotting scope in those situations.
At those extreme distances, and spending long periods of time behind the scope, I much preferred the angled scope. Way more comfortable to me, plus I could keep the tripod lower which was helpful in the wind and the high magnification using a light duty tripod and head. I also rotated the angled scope body countless times to fine tune the viewing orientation and essentially expand the viewable area without having to move the tripod or reposition myself. With a straight scope, I would have had to physically reset the tripod, and reposition my body, all those times. Not a deal breaker, but I appreciate less movement and less fiddling especially when whooped from climbing or dropping elevation. Nice to be able to just sit and relax, and "peak around the corners"!
