As someone who has spent far more hours with a trackball, and has been using them for over 2 decades. They are fantastic. Great for avoiding RSI. Best mouse you can use outside of a standard desk environment including standing, or at a couch.
But they aren't good for FPS games.
I just use a controller and I don't play competitively.
Feel like you'd have a better time buying a console IF you ONLY wanted a controller AND you wanted to only play competitive PVP games. Neither trackball nor controller can compete without some kind of aim assist.