It is not that all women are on a higher spiritual plane than all men. Women have an easier time earning olam haba than men because their floor is lower and they have less variance in spiritual achievement.
Mashal l’ma hadavar doma:
Women are like professionals, doctors and lawyers. The average doctor or lawyer will have a pretty decent salary and the top doctors an lawyers will have a fantastic salary.
Men are like businessmen and entrepeneurs. On average they will earn less than the doctor or the lawyer. But the best will far out-earn the top doctors and lawyers while the worst go bankrupt.
More mitzvos means more opportunity to grow and gain spiritually but it also means more opportunity to fail and fall.