I've managed to play slow-paced FPS'es with the trackball (e.g. PUBG) and remain - well, not "competitive" exactly, but not total trash either. You can generally dial it in for great accuracy but slow turning, or less accuracy but fast turning. But not really both at the same time, unlike a mouse. (since there you can your elbow for large movements, and your wrists for smaller ones) With the latter option, you would not be able to hit small targets quickly. In terms of desktop use, you can generally find a balance where it can get across the screen in a single swipe, but you can still hit a button immediately, so it's an OK trade off for me.