I was watching several youtube videos demonstrating stepper motors with built in encoders with closed loop drivers. On first glance it looks good, they have all advantages of standard steppers plus more. In such systems they advertised as can be cooler running and have more torque on higher RMPs, and the prices looks quite acceptable (I checked against stepperonline.com). Could those drivers be used for usual CNC routers, do they have real advantages?
My main concern is as following. If such motor loses a step, then it may be corrected by driver and as a result the motor succeeds. Fine. But let say the router was cutting a circle, so two motors doing their work synchronously, and one motor was doing fine and another lost the step which was autocorrected by motor driver. Are such corrections fulfilled in timely manner so the effect will be unnoticeable or it may cause significant deviations in tool paths?
What your thoughts and experiences on that matter?