I personally use mouse 2 since I actually started playing games on PC Only thing bit inconvenient to some ppl(people) might be my movement setup F2 = +forward 3 = +back 2 = +moveleft 4 = +moveright TAB = +duck
I bind jump to mouse2 only if I need mega ultrammmonster vertical rocket jump. And to mouse1 on strafe maps with little tiny stair double-jump in big speed.
+forward = R +back = F +moveleft = D +moveright = G +moveup = mouse2
Always using mouse2 lead me to believe the brain has a higher chance of heightening its ability to control the coordination between your hand and eyes. In layman's terms: you jump faster.