The Most Powerful Women franchise, just a decade old, is already Fortune’s second biggest after the Fortune 500. Amazing, isn’t it? This fact attests to the power of women in a year when so many powerful women – including Hillary Clinton and Morgan Stanley’s MS Zoe Cruz and Lehman Brothers’ LEH Erin Callan – got so close to the top and then fell. Even so, the power of women in business and beyond is clearly expanding. And Thursday we celebrated with the second of our nationwide MPWomen dinners, this one in San Francisco.

Quite a turnout. We had the top women from companies as diverse as the Gap GPS , Wells Fargo WFC , KPMG (thank you, KPMG!), and the Silicon Valley gang including Facebook COO Sheryl Sandberg, senior venture capitalists from Kleiner Perkins, Google GOOG Asia-Pacific/Latin America boss Sukhinder Singh Cassidy, and eBay EBAY SVP Stephanie Tilenius. She has run just about every part of eBay and could lead the entire company someday. That’s what former eBay CEO Meg Whitman has told me.

Cassidy and Tilenius, along with new lululemon athletica LULU CEO Christine Day, were on the Rising Stars panel that I led before dinner at the wonderful SF restauarnt Jardiniere. As usual, the questions from the audience were much about how successful women display power. I asked the three up-and-comers whether they believe that the acceptable band of behavior is narrower for powerful women than for men. Essentially, they said no – though Tilenius remarked that she wished that Hillary Clinton had campaigned more like a woman than a tough guy.

On this issue of female leadership style, there’s a generational divide. The debate began as soon as we sat down to dinner. I was sitting with Genentech DNA president Susan Hellman, Cisco CSCO chief technology officer Padmasree Warrior, SAFECO CEO Paula Rosput Reynolds, and other influential women spanning two generations. The older women generally insisted that they, throughout their careers, have been forced to behave a certain way – to rein in their aggressiveness and tone down their style.

This is true particularly in financial services. But Genentech’s Hellman, a former practicing oncologist who is now the most powerful woman in pharma, said that in her business, women aren’t so constrained. In science and medicine, the guys usually don’t even notice your gender. If you’ve got brains, you succeed.

P.S. Do you think that the band of acceptable behavior is narrower for powerful women than for powerful men?