No doubt that the linear scale is better if there is negligible motor to screw backlash. Some of the fancier systems out there have dual feedback, one device on the motor, coupled with another one on a scale, I suppose. I don't know what logic they'd use to interpret the two feedback signals, but it should be pretty awesome performance.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)