I am looking at a used Exmark WB. It's a Turf Tracer 60" w/ ECS. One thing i don't understand are the controls. Explain these to me. Are they not infinitely variable. There is a lever in the middle with N and 1-5. This is the only hydro that i have looked at like this. How do they compare to say a Gravely Pro-Steer or my old Snapper Hydro Pro (bout the same as Gravely's Pro-Steer)??