Fo rmy case, that's would be a dilemma as I own the 500mm AIP already.
Mostly the fear of losing sharpness.
But I can't say I would never go for the 200-500mm, Most pictures I saw on line so far are very decent.
And this zoom has 2 main assets :
# Very light;
# Vibration reduction.
However, it's versability is not a criteria for me : most of wildlife photographer will use it at its maximum focal range (500mm). So, better to have a prime, like the 500mm AIP :
# Less optical issues if you add a focal converter.
# It's heavy indeed. but still portable : I carry it miles hooked to my belt (with the Df mated on it). Hence no backache.
# You always find a support in nature, against a trunk of tree. a fence, a stoned whole (not in a desert, though !), so no tripod needed.
# No maintenance for VR or integrated AF motor which is so expensive.
# Shooting birds in flight is not impossible (if they are not too small or too close). Yet the zoom would make better job with its AF, I have to admit.
And I think the zoom will be more resalable.
So, if you haven't one of these lenses already and if you are not a specifically wildlife photographer, go for the zoom.
Few images with the 500mm AIP :
# 1 Cranes on the field. Very, very shy birds. Taken from my car, the lens resting on the window;
# 2 Stilt, hand held;
# 3 Stilt chick '' ''
# 4 Snipe.
