I agree with the other comments and add that focal length choice also depends on your use and your favourite subjects.
For birds or small subjects, 600 mm is perhaps the most obvious choice, while it is not mandatory for mammals.
It depends on the type of photography you generally do. If you shoot mainly in the hide with a tripod, a long and heavy lens like 600 mm doesn't affect the handling compared to a 500 mm. If you use it in the car, it is different because it is more bulky, inside a relatively small and less comfortable space.
If you move a lot on foot, the 500mm, even better than the PF, is probably the best choice.
Like many of those who have already answered you, I also went from 500G to 600 FL to have a longer focal length without necessarily having to use the multiplier, while for trips abroad not purely photographic, for hiking in the mountains or in the middle of the woods, where size and weight make the difference, I use the 500PF and I'm pleased.
Also, consider the learning curve required to go from a zoom to a fixed lens. Framing with the 200-500, which is quite light and in any case allows you to frame first at a shorter focal length and then zoom in at a later time, is not the same as immediately framing a subject with a handheld fixed 600mm. It takes some practice.