I could be very very wrong, but I think they would all theoretically cut any material. The difference would be the speed they could cut at. Also depends upon the thread on the rods they are used with. I recall seeing an amusing post somewhere on the zone that referenced using a tiny motor to lift the pyramids in Egypt......just have to be geared WAY down and run REALLY REALLY REALLY slow!
Also, what exactly are you cutting with.....a stepper motor for a waterjet wont actually have to 'drive' anything through the material like a router would have to do with its cutting head. Likewise for a plasma cutter, the steppers would only need enough torque to overcome the weight of the gantry and friction.
I imagine cutting marble would be real slow....and need lots and lots and lots of coolant.....but not sure if marble can be economically cut without the likes of waterjet.
Maybe tell people how fast you need to cut each different type of material.
Sorry Im not more help.