Get the Flex 3401 VRG...PERIOD. It is the only Forced rotation DA on the market. It is more versatile than the Rupes. It corrects better than the Rupes, you can get 4 different size backing plates for the Flex to where you can get 4" Pads all the way up to 7.5". The Rupes is limited and does not have many backing plates options.
Additionally, if you do not have Rupes pads on a Rupes you will rip the pads frequently...ie Lake Country, Buff & Shine...etc.
The Rupes is still a free floating DA so you can stop the Pad or if you are polishing uneven panels it will stop.
Additionally, the Rupes cost more than the Flex.
All that I have said has probably angered the Rupes clan....so be it. I will ALWAYS think the Flex 3401 VRG is better than a Rupes.