Enve 6.7 is only 2mm deeper in the front than the 404, and 12mm in the rear, so not really huge. Like Zen says, the 3.4 is probably the better all around wheel, but the deeper wheels aren't a bad choice either.
The Enve's are stiffer, more stable in crosswinds, and their warranty service is excellent. Never any warranty hassles with wholesale orders, and they always seem to give the customer the benefit of the doubt, vs Zipp, who from my experience just assumes its your fault and makes you prove otherwise.
I thought we had determined that to be a "make the marketing fit the data" point by Enve. Their overall steering torque is higher than Zipp, but it's more linear beyond some unspecified yaw angle (because who needs to label the x-axis). I have a big issue with how dishonest they present their data given than they just plugged "303 Firecrest" into the data after it came out rather than actually testing it (the previous 303 was tested, not
a Firecrest, as they claim).
I think a lot of the braying about this or that with Zipp is completely overblown , but I'd still go with Enve just for being able to choose my own hub, especially given the small cost difference (Enves also seem to retain their value better).
e: also, how have people not learned to use the wheel sub forum yet?