The AS have a freakishly high percentage who joined the BA (likely due to recruiting in the Tower). The Aiel and Sea Folk are far less likely to have so many DFs in their channeler ranks and the Suroth already told us how few Sul'dam are DFs. The Kin have no DFs in their midst or the BA would have known much more than they did about the Kin.

I would be surprised if there were more than another 50 women outside of the BA who are DF channelers. The Shadow will be at a large disadvantage in Channelers. Maybe 200 Men and 200 women at most v. literally thousands of light side Channelers. The Shadow will need the advantage in sheer numbers, thus they probably have millions of Shadowspawn.