Gear head lathes all leave echoes of the gears on the surfaces of the work,unless you can afford the very high high class lathes like Dean,Smith,and Grace,Monarch,etc.. My 16" Grizzly leaves the marks. Gear head lathes are easier to change speeds on. On belt driven lathes,you have to manually move the belt from one pulley groove to another to change speeds. However,you will get a smoother finish. I have a Hardinge HLVH,which is all belt,but has a mechanical system of variable diameter pulleys to change speeds at the touch of a button,plus a 2 speed motor. I can get from 135 to 3000 rpm by pushing a button,or shifting a lever.It gives beautiful finishes due to having class 9 high precision spindle bearings,and it has a 3 phase motor. 3 phase motors run smoother than 1 phase. A 3 phase motor gets 3 impulses to turn per 1 rpm. A 1 phase gets 1 impulse per RPM. This smoothness can be seen on the workpiece because the 3 phase motor imparts less vibration to the lathe. However,my first decent lathe was a jet 10 X 24",and it was single phase,and gave extremely smooth finishes,too. Not quite as nice as the HLVH,but very nice. I wish my lathes were all 3 phase now.
I actually ran a 13" Dean,Smith and Grace lathe and it did not impart any gear echoes on the steel bar I was cutting. It is the Rolls Royce of lathes,though,with super precision ground and polished gears. Also,an incredibly massive lathe for its 13" swing. It's bed was too worn to suit me,though,so I passed on it.
