Hardly any current AFV still uses steering levers, except maybe the M113.
Anyway... Mouse or stick, it's a matter of taste, really. A joystick isn't needed, but can be more convenient for certain modern vehicles that have many functions on the control sticks, especially those like CV90/40, CV90/35 with their programmable munitions - also remote weapon stations.
Mouse control is said to be more precise and easier to aim with, joysticks are said to be faster in some situations.
IMO, if you have a stick, try it. You you don't have one, don't worry.