Given one would benefit from the extra range-
So from what I've read the 70-300mm is as sharp as the 70-200mm f/4 IS through 70-200 at the minimum, perhaps even further out. Also, while the 70-200mm is f/4 constant, again my understanding is the 70-300mm is f/4 up to 200mm.
So, even if the 200-300mm range is ever so slightly less sharp and is also f/5.6, since the overlapping range between the two lenses is basically the same I am not seeing any disadvantage with this lens vs the 70-200 f/4 is... Thoughts?
because the 70-300L is not f/4 up to 200mm
it is f/5 by 200mm (OTOH the 70-200 f/4 IS is a slightly slow f/4 at 200mm, more like f/4.25)
the 70-200 is also a bit lighter, you have that constant aperture
but yeah the 70-300L is good, I did end up selling my 70-200 f/4 IS after getting the 70-300L, not needed to swap on a TC is nice, that is SUCH a pain (plus, if you still swap on a TC, on the 70-300 it gets you to 420mm!!)