The presumption was that you knew that I9 spokes can't be used on silly j-bend hubs. But for the same rim, and same build, the I9 wheels will be stiffer. My I9 wheelsets are 32H laced to 729's and I also have 32H Hadleys laced with straight gauge spokes to 729's and there is a noticeable reduction in lateral deflection on the former.

Back in the 90's, CK was far and away the best mtb hubset you could get. Since then, other companies (Hadley, I9, profile) have begun offering hubs of comparable quality. They're all great hubs and all proven. But I would happily trade the often touted (but still breakable) ring drive of the CK for the 60% quicker engagement and stiffer wheel of the industry nines, because those two factors make for a better riding bike.