Are there any noticeable differences? Seems like the only difference between DSF/Zen and XMCS. Also wanted to ask what spoke count and spoke width you could would recommend for a lightweight rider. Carbon spokes
That's a tough question, I don't think there's a legit answer.
These hubs have probably no noticeable differences for the rider, you might need to lab test them to get to the point where you know which hubs are stiffer. With modern CNC machines they will be equally acurately milled. For a decision, comparing bearing size might be of interest. Bigger bearings last longer, but come with a weight penalty.
And if you build your wheels yourself, you need to decide if you want to go for 20 spokes or 2:1 spoke pattern. I'd always prefer a classic spoke pattern with 24 spokes for my own builds.
But still, the big flange from the R2 rear hub to get equal spoke tension is very interesting.