IMO a scope with an angled eyepiece is MUCH more versatile than the straight version - especially in the prone position. I have a Kowa scope that will rotate 360° in it's mount which allows you to have the eyepiece sitting sideways as well. With the scope low to the ground you don't have to get directly behind the scope and it can sit off to the side somewhat. With that setup, you don't have to break your prone position to look through the scope.
Along the same lines, if you are shooting from a bench using the angled scope, you won't have to crawl over the back of the bench to get to the eyepiece.
For what it's worth....
Scroll down to the bottom of the page for some illustrations:
Long Range BPCR Spotting Scopes