So for a little background; I previously used a Nikon d7100 matched with a Sigma 150-600 Contemporary lens with mediocre results, which I blamed primarily on operator short comings in technique. I also came into an older Nikon 500mm f4 af-i lens, which performed well with the d7100. I have since moved to a Nikon d500 and began with the Sigma lens, with so-so results. I had not used the 500 f4 with the d500 before today. For the past few months I acquired and have been using a Nikon 200-500 f5.6 lens with decent results, but still convinced myself that the limiting factor was still my technique. I have been considering selling the 500 f4 because I have been enjoying the new lens so much and didn't really think I was giving much up by do so.
Today, I had eyes on a Coopers Hawk in my backyard so I decided to break out the 500 f4 and hand hold it! I forgot out heavy and cumbersome that lens really is. However, I practically was peeing all over myself once I locked focus on the hawk and began clicking away! The additional stop of light entering the lens and quickness of the focus was remarkably better than with the 200-500 f5.6. Now I know that a prime lens is always going to offer the best optics but I figured the newer technology would win out over the 20+ year old mammoth of a lens.
I do really like having a zoom for bird photography and I like being mobile. However, after re-using the 500 f4 lens once again I am now questioning how and when I would use it in the future. It is so big and heavy and almost always must use a tripod which is not an opportunity I get very often. I am just surprised at how under-impressed it makes me feel about the optics and focusing of the 200-500 f5.6 lens. (It's funny but the person I bought the 200-500 lens from claimed it was not a fast enough lens for their use, which was primarily waterfowl in action.)

Maybe my strong desire for an affordable, enthusiast level zoom lens to be better than what I would ever need is not to be. Has anyone else experienced this syndrome?
I feel I would have better off if I had never used a 500 f4 autofocus lens in the first place! Curious if others have experienced anything similar?