OK, first, the original question was about a "RO" (random orbit)
not a "DA" (dual action) BIG DIFFERENCE!!!!!
Most air sanders are DA's, which spin fast (RPM)
and oscilate slow (orbits)
Most RO sanders are electric,
they spin much slower and orbit much faster.
Both sanders come in mostly 3 different orbit sizes
usually from 3/16" to 3/32"
All these combinations makes a big difference in how they sand.
A DA will be more aggressive than a RO.
I find a RO with a small orbit and slowed to it's minimum speed (RPM)
will sand clear longer before loading the paper.
The faster spinning DA's tend to heat it more and clog.
Even slowing them down, which helps, doesn't go as far as my RO.
Electric RO sanders come in two types too.
The palm sander type is for fine finishing and mostly for woodworkers,
but the "right angle" RO's are made to be more aggressive by putting out
higher RPM's and work good for clearcoat sanding and fine polishing.
this all gets confusing but the specs for RO's are on the nameplate
and usually list "OPM"s (orbits per minute) so you can compare.
I like the Porter Cable "right angle" RO for clear sanding.
It's the same tool for sanding or polishing.
http://www.deltaportercable.com/Products/CategoryOverview.aspx?catPath=4272.4288.4291
Here's the "palm sander" RO which I only use for wood, it's just to
slow for automotive.
http://www.deltaportercable.com/Products/CategoryOverview.aspx?catPath=4272.4288.4290