@Rasp
The vertical mouse I tried was the logi MX Vertical, but I'm not sure DPI is the issue for me.
I think it's just the way you use a trackball is different from how you use any other kind of mouse, and I've found that I prefer that.
With a trackball I don't move my hand very much at all, maybe I move my wrist a bit but my hand is pretty much stationary. With a mouse I have to actually move my hand to get the cursor to move, and I realize that I don't like that very much.