I doubt they are stronger than the EN521. The EN521 is after all the same width, a little taller, and what.. 60g heavier, or 40g heavier than the white Stans? That weight or some of it must surely equate to strength? We are talking Mavic here.
I wouldn’t select a rim purely based on price. Particularly if that choice is between the EN521 and DT5.1 (EX500) and Stan’s Flow. They seem equal in quality terms to me. Maybe the French company Mavic are a bit better value, or there is a higher premium to be expected for Swiss goods?
I am trying to select a second set of Hope Hoops. I was toying with another set of DT 5.1’s (EX500).. but I haven’t ruled out the EN 521.. I would consider Stan’s but they seem a tad on the light side to me, I see them as an even racier version of the DT5.1 (EX500) however, and at 15stone I think maybe they are pushing the envelope for me. Though maybe this isn’t true. Dunno.