I'll start. Did you know you can run a headless version of JD2 on a raspberry pi? It's not the greatest thing in the world, but sometimes its nice to throw a bunch of links in there and go to sleep.
They each have their benefits. I use both. I only expose Overseer externally. It’s nice and easy to pop it open and add a new movie/show while I’m away from a computer. Then I’ll use one of the *arrs when I need to do something more advanced or I’m using a desktop locally.