For me it's more comfortable, reduces wrist strain. Not everybody agrees, YMMV, etc.
I been using a trackball since the very beginning of 2000 when I bought one as a wth, its but $20 from CompUSA, and never looked back. Now I use what is the best IMO trackball made since my old Kensington mechanical broke on me and its called a ELECOM HUGE with mappable buttons up the wazoo
Days of picking up, setting down, getting killed in that micro second it took to reposition, or mouse come off the mat screwing up my shot in the heat of the game
There is a slight learning curve to it, but once you get it, no other mouse will do. Best of all really is, it takes no space because you leave it where it is, do not move it one bit, so a reverse of a typical mouse, which is great, for no large mats, or room on the desk, or small room on mat/desk making several hundred repositions while gaming or surfing.
As for Keyboard, nothing like a 20 foot extension usb wire to a powered usb hub, that sits on the floor or under a carpet/mat so no one can trip over it.