I think the M952 will have a slightly narrower cage to work with a 9 speed chain. Both will work, one will be a bit better than the other. I've run a mix of M950/M952/M970 on different bikes.
I built a set 25+ years ago and remember it being the hardest hub to work with. Getting the spokes to seat in the flanges was really tricky. Take your time with the build.