Don't have any experience with random orbitals that go up that high, although I've used one that can do 6,000 opm (the lowest of your range) with no problems. Posts that I remember reading seem to suggest that there's no real downside to the higher speeds beyond some products flashing too fast (usually
Klasse AIO - which I've experienced firsthand).
My only other thought is that the ETS150/3 is only 2.6 amps, so it might bog down earlier than some of the right-angle sanders if you put a lot of pressure on it? The Rotex models give you the option of having the direct drive mode in addition to having more power, but it depends on how much correction you plan on doing, I guess.
Festos aren't cheap as a RO used exclusively for buffing/polishing. I assume you have one because of woodworking and are thinking of using it for automotive work as well?