Nice topic.
In my opinion OP, you're only looking at 'one side of the coin'. I've decided for the Flex (to buy first) mainly because it's 1 machine that paired with larger or smaller pads (changeable backing plate to use even 4" pads) will handle (mostly) any entire car by itself.
I've not had any issues regarding machine bog down or lost of rotation with my actual G220v2 DA, even reading many cases relating lack of power and pad rotation on this machine. I've started using 6.5" pads, and even with them, pad rotation under pressure was never an issue.
I mean, the technique to maintain pad rotation basically lies in positioning the polisher to get the pad flattest you can on the surface, and for many curves you have to position it properly, some times contortion yourself, crank up on speed, but you can do it!
Another advantage I've seen on Rupes system is that pressure is not a very determinant factor, like on smaller throw DAs. With that in mind, maintain proper pad rotation may be less of an issue. Product quantity for proper surface lubrication maybe always in account when having pad behaving less than optimum way.
What I mean, if I only get a Rupes 21 (instead of the Flex), how would I correct side mirrors, even with a 5" backing plate but a 21mm throw? Ah, they have the mini Rupes for that, and (hey!) it's an awesome machine!
I've talked about it in some other topic, if someone has the whole Rupes line of machines (21, 15, 12, mini, etc) it's fair that guy won't need other brand / size machines / backing plates.
I believe we're reading many reviews from 'New to DA' users that acquired the 'new kid on the block' and are relating the same lack of rotation I've read on G220v2 some time ago, but now about the Rupes.
One good thing about INTERNET is that we can read EVERYTHING but trust only what our EDUCATION allows. I admit, reading Rupes can stop on curved panels never went into account for me.
It's like: 'So you're saying Paul Dalton is struggling on curved panels with his Rupes?' lol, Come on!
Another thing I've talked earlier was regarding User's Fault. I've related my fault using some polish that were dusting and a pain to wipe off. Was the polish a lame? Absolutely not, the flaws were entirely my fault.
It's easy for one to come at a forum and flame any product or brand. The same way it's difficult for one to educate himself (a lot), and get enough time of 'HANDS-ON' experience before blaming a product or brand instead of himself.
I've decided for the Flex mainly because I can only handle 1 at a time, and I wanted 1 machine to 'do it all'.
My G220v2 worked very nice until I had to start 'abusing' it. Now I have to submit it to HEAVY and FAST work (against the clock), and this was not what the machine was intended for.
If I were to stay at weekend warrior category, maybe I wouldn't even exchange my Meg's DA.
Now that I have more work to do, I've decided on the Flex FIRST, but that means the Rupes will come when I find the NEED for it.
By the way, if someone at Rupes will be reading this, please, contact me and I will spin your pads on any panel, record on video and place here.
I just won't promise I'll correct side mirrors with 21mm throw and 7" pads!
Thanks for reading,
Kind Regards.