This isn’t scientific but it seems to be harder to dent a Flow Ex but easier to outright damage them- I beat a Flow to death and replaced with a Flow Ex and it picked up 2 significant dents into the rim bed within half a dozen rides- both big hits but still, the old ones took big hits too. OK, it’s on a dh bike ridden by a knobber so that could just be bad luck and clumsiness but I’m not convinced. The old Flow was denty, sure, but I must have straightened out a million dents from the old rim and it kept on going- cracked at the valve hole eventually.
I dunno, maybe their relative softness of the bead was acting as sacrificial protection for the actual structure of the wheel. Always suspected that was why my 721s cracked so badly, too hard for their own good maybe. (I stopped counting after I got to 5 cracks!)
So all in all I’d be happy to buy either again but I feel like I had better service from the old Flow.