Last year for UAE ENVE’s lead design engineer built an algorithm that determined the 4.5 would be fastest on anything other than a sustained, super steep climb like the Angrilu https://enve.com/...s-started-months-ago With the new straight pull hub this year it dropped more grams. If memory serves UAE does 28/30 and goes up for cobbled classics (though they might have gone to 30/30 as daily drivers).

I have both the 3.4 and 4.5. The former I use on gravel bike and is very user-friendly. The latter is on road bike and 50 grams heavier but faster. It’s a little more grabby in bad crosswinds, but will be far more rideable than 5.6; it’s a different rim shape and also wider. I ride it with 32s and it’s a bit of a Goldilocks wheelset—fast, handles really well and fairly light.

So which one? Tough call. If you want the faster setup then 4.5. If user-friendly is greater concern then the 3.4. The weight difference isn’t significant enough to be a major consideration, IMO. I think Ferris rode the 3.4 only for Fleche and maybe a mountaintop Tour stage last year.