Yeah SuperPi seems slow and sporadic on 10, depends on the build maybe. I've checked 3 times in the last few months, first time 10 was pretty close to 7, next time 32m took 40m+ and was super slow, now this version is about 50s slower than 7.
Looks like I'm not alone then, Windows 7 completes 32M about 1 minute faster than 10. A couple months ago I also had an issue where 10 took ~40 minutes to finish a run which is insane, but that seems fixed now.