Here is an interesting question - something to try an experiment with. Hold a palm sander upside down against a bright, uniform background and turn it on. (Careful!) Examine the edges of the pad. Does the pad move in a plane? That is, does the "blur" you see caused by the pad movement stay in a flat plane or is there some up-and-down component to it? I tried this with a cheap finishing sander and it seemed to be flat, but when I tried it with my new Bosch 1295 I could see that the pad did not stay absolutely flat. There was a noticeable up-and-down component to it.
Any comments or experiences?
-Ram.