Definitely simpler to program, as you know exactly where the servo is. It depends also on your actual application. Steppers tend to provide better speed control and holding power than servos.
Do note that the servo library only allows for 180 steps (common servos are 180° ones and you can set them per whole degree, no decimals). If that 6-turn servo reads 180° as 6 full turns, you're limited to 12° steps! So do carefully check how that one is controlled and how the servo library would deal with it. By setting the pulse length directly you do get better resolution.