Walt,
I started with the ETS 150/3, because I wanted the lowest vibration available. I was sick of tingling hands. I found it to be a bit slow at first, until I decided to drop down and begin a grit lower than I guessed. That makes it work quickly enough for and amateur like me. A pro like you may need faster action, so the /5 might make enough difference to make it worth your while. The finish left by the /3 is outstanding, as you've probably found out. I don't know how a /3's finish compares to a /5's. Go to Woodcraft at Virginia Beach and ask Festool Mike to test drive the /5. Take some samples of wood with you to play with.
Stripping old paint with the /3 is more of an ordeal than sanding bare wood, though coarse grits, good choice of abrasive, and patience will get the job done. I added a RO90 to my arsenal, and it's a good companion to the /3 for the rougher stuff. It's ideal for frame-and-panel stuff, which I expect you do a lot of.
I shied away from the RO 150 because I didn't know how to handle it. Since then I've tried several demos, and now I see what all the fuss is about. Don't say never. It's a strong but gentle beast.
Cheers,
Crox