There seems to be a difference of opinion with button layouts, but this is a unique one; do you prefer that a game:
A) makes the move button also the sprint button
B) makes the move button also the crouch button
In the former scenario, you can start sprinting at will and without hitting any other buttons. Additionally, you can always tap the other crouch button, while running, to go into a slide. Lastly, you can use the camera stick to pan around, as you run.
In the latter scenario, you can walk into a crouch and duck, while moving. It does create the risk of momentum-killing crouches. With regards to the camera, you can only walk and pan around.