Hi David,
The answer is "it depends" :roll:
I've been out at the Cranberry Marsh hawkwatch many times, and there are many good birders out there. On one particular day, several hawks were called as "Red-Tailed" and actually hovered right over us for a while. No one was "sure" about it, even tho there were several pairs of eyes on those birds for a good while.
I took a few shots with my camera anyways. After getting home and doing a quick contrast adjustment, the translucent crescents were clearly visible - Juv Red-shouldered Hawks.
At other times, I know I'll get a better look with the bin's than the camera, so I'll reach for the bin's instead. Especially so if it's a little bird in the bush. Bin's are also better when there are several birds in the same field of view.
So I guess my point is, sometimes it's easier to identify certain field marks from a photo, especially if you only have a fleeting glance, or you don't have enough time to check the field guide.
A lot of this will also have to depend on your skills as a birder as well. Many of the good birders I've met don't even need bins to id the bird. For the novice birders, pictures help _alot_.