Servos Torque VS speed. or both?
 

Hey guys!
Was just wondering if Speed on the Steering servo is REALLY important or not?
I currently have a Hitec HS5645MG digital which is rated at 10.3KG and .23 secs (for 4.8v cant get specs for 6V)
so basically i got the torque! but not much speed. i know it all depends on the drivers but just wanted to get a general overview or how many people find fast steering servos easier/fun to drive. or is torque more important?

Also whats the best and cheapest throttle servo? need something fast but dont need torque but i can only find fast servos with alot of torque as well (8KG+)

Also does exponential help with the speed of the servo? i see a difference as it makes the servo travel say you pull 10% on throttle trigger the servo will travel 40%.

Thanks guys!