First of all you should match specifications of both, one the machine which you are going to purchase and second of your job, you want to do on the machine.

Centre height of your machine must be match with O.D. of your job. Swing over bed and swing over cross slide should be select as per your job.

Spindle bore should be with such dimensions that your job O.D. may be pass through it easily if it is necessary.

More Width of bed gives more rigidity and sturdiness to the machine. In heavy work it is necessary.

In belt driven there are two options, flat belt and V-belt driven. Flat belt is slipped when there are over capacity work taken on the machine and V-belt is sturdy design to remove some what slipping actions. And in Gears drive (Geared Head Lathe Machine). It gives more power to turn as well as it is suit for more speed and feed and resultant it increases productivity and low electricity consumption.