I conducted a backyard test. Took the same image with both lenses, with the 300 f4 (@ 5.6) and then with the 200-500 set at 300mm wide open @ f5.6. Minimal post processing done. What do you think? Here they are, side by side: (click to see the original)
https://c1.staticflickr.com/1/758/22...fff8b25d_c.jpg https://c1.staticflickr.com/1/676/22...60a57d29_c.jpg