Senior women are often heavily over-asked for mentorship by younger women. They have less of everything to spare — less time (often carrying domestic load), less political capital to spend on sponsoring proteges, less sponsorship from their own peers. Their mentorship is valuable but constrained.
Where senior women bring unique value
Lived experience of specific challenges (negotiation as a woman, navigating maternity leave returns, dealing with overt and covert sexism). Networks that include senior women in other companies. Empathy and specific advice that male mentors can't provide.
Where cross-gender mentorship adds value
Senior men often have more time, political capital, and sponsorship to offer. Many are genuinely supportive of female career advancement. Limiting yourself to female mentors only undercuts your potential support network.
Build a board of mentors and sponsors that includes both genders and varied seniority. The most effective career support is usually a portfolio, not a single mentor.