Edge test, 7D,300 2.8mm ll vs. 300mm 2.8 l
Verdict for me as a birder.
Optically? on a 7D cropped body. Not worth the upgrade period.
I would add one thing - for those who do not have the mrk 1 - better get the mrk. 2 which will have better repair odds further down the line. But for pure optical performance how much more could even be expected over the old version?
Weight? worth it for a walk around lens.
OS? wroth it for a walk around lens.
These are the two reasons I'm looking at an upgrade right now. Also checked out the Nikon (if going for the D800) - the weight difference is staggering if you use it as a walk around lens (which I do).