Have never used it, but if only 1 machine I would take a hard look at this one:
Makita Bo6040 Polisher
That is pretty nifty, if they had a 3" version I'd be more interested right now, seeing as I own a rotary and a DA. It says it tops out at 670 RPM, my rotary starts at like 800. I guess you could have a lot of success with MF pads, but foam would probably have a hard time correcting.
I'd pick my makita rotary with soft start, but I feel like the flex is probably a better machine I just haven't tried it.