When I designed my first machine tools, I used pretty much what was handy. That meant the stepper motors came from "ye olde electronics shoppe" and with little information beyond amperage, max torque and stator inductance.
Very soon I became a speed demon : I live in an appartment building, so if I'm going to make noise with a machine tool the faster the cutting is done, the less likely the neighbors will come banging at the door. I also like the idea of cutting fast and without any coolant or lubricant, because it's a lot cleaner. And it just looks damn cool
Eventually I reached the limits of what my machines could do. One important problem was midband resonance. I installed viscous dampers but it didn't help where I thought it would. And Gecko stepper drivers aren't sold in France. So I had to invest in a better solution.
Brushless AC servos were my first choice. They are known to have no midband resonance and are very fast. They are also very expensive. After some Googling, I found out about the EvoDrive solution : a stepper motor driven like a brushless AC servo, complete with encoder and integrated closed-loop driver.
At the moment, the largest unit is based on a NEMA-23 frame motor (the ST-23), and plans are being drawn for a NEMA-34 unit.