For flat surfaces, this Porter Cable-7346 dual action grinder is the best tool that I have ever worked with. It’s kind of half way between a big angle head grinder and an orbital. The angle head grinder can get huge amounts of work done, but a moments inattention can do a lot of damage. An orbital takes forever to get anything done. This unit can remove a lot of material but is easy to control. And being electric, you don’t have to wait for the compressor to catch up.
http://www.amazon.com/PORTER-CABLE-7346-6-Inch-Random-Sander/dp/B002EQ96NK
With a lot of sanding in front of me, this caught my eye. But I’m wondering if it would be an worthy upgrade from my model which may just be an earlier version. I have the 7336 random-orbital.
I don’t know what a 7336 is but my unit here was basically a variable speed anglehead grinder with orbital action as well.