What makes the 200-400mm Nikon lens that much better than the 200-500mm lens? I know one is F4, the other F56 but that can't be it... Just wondering.. Anyone used both? Thanks
Better in what way? The 200-400 should have faster AF performance because more light is available to the AF system. Likewise, most lenses are not at their sharpest when shot wide open, so the 200-400 should be sharper at f/5.6 than the 200-500.
Getting that lens to allow more light through typically means there's more expensive glass elements and heavier construction, which also leads to the price delta. I would suspect the 200-400 to also be heavier than the 200-500.
But, if all I have is $1500 to spend on a super-tele ... the 200-500 is the best lens because I can take it home with me.