I have an RO150 and an RO90. They're both very versatile and reliable sanders. When I'm not using the overhead boom with dust collection hose and power cord for another Festool, my RO90 hangs on it, just to the side of my work bench and table saw, ready for immediate use.
Festool publishes extensive advise on choice of sandpapers. If I understand their specs, in spite of the names they assign them, they all use Aluminum Oxide abrasive.
An older Festool document can be found on the Jamestown Distributers website.
This document does not cover their latest line of abrasives, called Granat. These are a bit more expensive than their other lines, but are more versatile. It seems that they were designed to be used by unskilled labor who can't read and comprehend more than one design parameter (e.g., grit) at a time. They are excellent papers, but if you are sanding bare wood only, the Rubin papers are more economical.