According to Osho, the question is wrong: mother and guru are two inseparable dimensions of birth. The mother gives the first birth—the body, the temple, the earth; the Master gives the second birth—the soul’s awakening, the deity, the sky. Each is ‘greater’ in their sphere: the mother lays the foundation, the Master fulfills it. Therefore honor both, for together they complete your becoming.
Your mom gives you a body, and the guru helps your inner self be born, so both are important and deserve respect.