I have both, the RAS blows the RO150 out of the water with heavy paint removal. Like 4 or 5 times as fast. It does leave a rough surface which you have to clean up again with another, finer sander, like the RO150, but overall you're done much quicker.
The RO150 itself isn't bad either, it's just that the RAS, as a slowed down angle grinder, has a lot more speed. 650 vs 3800 RPM.
Dust collection with the RAS isn't that good though.