Roy C
Occasional bird snapper
That would be good but I suspect the number of folk with both the 500/4 or 600/4 and a SX50 would be few and far between but you never know. Until we find someone you will be stuck with theorising I am afraidIt would be great if someone with this lens and an SX50 could do some side by side tests at very long distances so we know for sure. Much better than theorising.
I do know for sure that the SX50 over extreme distances (say 150 yards+) beats the 300/2.8 IS +2xtc when shot from the same spot and cropped heavily.