1. Easier to get on target.
2. Easier to glass from above.
3. Easier to glass from a vehicle.
1. Easier on the neck.
2. Easier to glass up.
3. Easier to use with multiple people of different sizes.
4. You can use a shorter/lighter tripod.
5. Supports a digiscoping setup better.
I use angled, because most angled scopes have a rotating color that more or less evens the field with the straight, except about getting on target easier. After some practice, though getting on target with an angled scope is second nature, at least for me.
i just switched from a strait to a angled and i will never go back. other than what is listed already the biggest advantage is with an angled spotter and a good head pistol grip head on my tripod i dont have to constantly reset up or shift around to glass a area. theres so many ways you can adjust the spotter and head that you can glass over 180* from the same siitting/tripod location. try looking 90* to you left or right with a strait spotter and not shifting your body or tripod around. its really a no brainer once youve used a good set up