The 180-400 is the best performer in this class, but it is frightfully expensive.
There was a point in my journey when I owned the 80-400G, 200-500E, 300PF, 300 f/2.8 AFS, 200-400G, and 500PF all at one time. Now to be clear, some of this was for my wife, some for client use when teaching, and some up for sale at the time. Two years later, I now have the 300PF, 200-400G, and 500PF. When my 500PF first arrived I did a comparison between the 500PF, 200-500E, and 200-400G... you can see the non-scientific results on my blog (
Link ). I generally use my 200-400 w/ the Z6, and like others, have found the prior focus inconsistencies to be gone. The lens is prime sharp between 200 and 340mm at f/4, and is very sharp at f/4.5 when shooting at 400mm. Originally, I used 200-400 on D300's, D3s, D4, and D500s (since 2014). I now use my 500PF on my current DSLR bodies, and have made the 200-400 a Z-camera telephoto lens... while the lens has its warts, I find the build, focus, micro contrast @ f/4.5 (and beyond), and bokeh to be far superior to the 200-500. It took me about 5 years of dual possession, but I have finally sold my 200-500mm lens. Until the Z 100-400 or 200-600 is released or I find the $11000 I would need to buy a 180-400, I'll keep shooting with the 200-400 on my Z6/Z6II bodies.
cheers,
bruce