Jeff, there are pros and cons each way. I prefer the straight because it allows me to get on game faster than figuring out the angle. For paper, it wouldn't matter much. Some straight angled units lend themselves to becoming bigeyz some day, angled cannot.
Angled is preferred when people of different heights have to share a unit without changing the height.
it's almost always the scope itself which is angled or straight. The eyepieces are interchangeable between either design.
Angle scopes are easier to hunker up to in position shooting with minimal change in shooter's position to have a peek. Straight scopes are more naturally 'pointable' at your target, so lots of folks prefer them.
I prefer the angled scopes, and mine has a little sighter tube to help align the scope when you first set it in place.
Suggest you go to a match, peek through a few of both types(after asking permission), and go from there.
Of more importance than angled vs. straight is eye-relief (how far your eye can be to still see a complete image). Generally, more eye relief is better than less. Get one with at least 20mm of eye relief, especially if you wear glasses.
The biggest thing to consider is what is the spotting scope going to be used for the most. Typically an angled eyepiece spotting scope is used for benchrest shooting, where the straight is used for hunting.
Angled eyepiece scopes can easily be used as big eyes setups. Angled has always been easier to use for me in position shooting. And I have no problem using it while hunting etc... In fact I like it better than a straight scope in hunting also since I can usually get into a much more relaxed position and use the scope longer that way.
But others continue to prefer straight. On the across the course highpower ranges and the Long range highpower prone ranges, I continue to see almost exclusively the angled scopes.