The communities are actually quite different. Cubietruck uses Allwinner and Radxa uses Rockchip. So one community is centered around linux-sunxi.org and the oth

The communities are actually quite different. Cubietruck uses Allwinner and Radxa uses Rockchip. So one community is centered around linux-sunxi.org and the other around linux-rockchip.info. I don't know the actual overlap, as I'm mostly interested in linux-sunxi stuff - but I doubt that the overlap is actually big/significant.