I think there is very little difference between the aerodynamics of the top front wheels. HED, Zipp, Roval are companies I trust to make great wheels. I'm interested in investigating Swisside more but I do not know a bunch about them. Zipp I think is overpriced. HED is by far the best deal. I was convinced that Roval may actually make the fastest wheel by a small margin. A combination of their white paper on the CXL50 plus their engineers' interaction here on the slowtwitch thread about that paper where they filled in a lot of the holes in the paper I thought was great - the data looked good. They seemed quite transparent about it. They actually tested rotational drag, not just translational (I'm not aware of any other wheel company doing that, or at least not publishing results). They did a lot of work on the shape of the hub. They tested spoke nipples.
So after that I bought a CXL64 front wheel. I think there is a chance that they are the most aero by a small margin, they are the lightest, and they are very high quality. I use a HED jet + disc in combo with my Roval.
I considered the CXL64 as well. The Specialized supplier (which I have a very good relationship to) was honest enough to say that it probably has little to gain. I agree, but can ask what price he can give on a front wheel. It is just 20g lighter, but has 21 spokes instead of 24, which might give aditional gain.
I know HED is good, and probably gives the best bang for the buck. They are, however, heavier which I dont fancy in a course like Norseman. A HED 3 Spokes would be super cool, but they dont have it disc brake version.
Zipp 808 NSW is probably one of the fastest as well, but at 910g, compared to 735g for the Roval and with 24 spokes I doubt it will be a faster option for me.
Any other options?
3 x Norseman winner - http://www.triallan.com
Quintana Roo - https://quintanarootri.com
Morf-Tech - http://www.morf-tech.com