The woman's bike with the sloping or swooping top tube is an obsolete relic. Don't buy one. The companies that are still making them are trying to cash in on retro looks or selling to women that grew up riding that style. The bikes are weaker. Besides, women don't ride wearing dresses any more.
There is no difference in the basic geometry between a man's bike and a "woman specific design." They both use the "double triangle" frame style. Some manufacturers claim that the ratio of leg length to torso length is different between men and women so they adjust the lengths of the tubes accordingly. Another manufacturer, well known for advanced engineering, claims that the ratio of leg to torso length differences are not significant and the real problem is that nobody knows how to fit bikes to shorter people of either gender.
Saddles are different. Men and women are significantly different in the "sit bone" department. Just go to a bike store and hold a woman's and a man's model (like the Terry Liberator X and the Terry Liberator Y) in each hand and compare them.
Setup is different, too. The shift and brake levers on women's bikes are usually adjusted to compensate for a woman's typically smaller hand.
All that having been said, try a man's bike. I've known several women who found that the woman's specific design did not fit them as well as a man's bike. It's all about the fit. A bike that fits is a joy and a pleasure to ride. A bike that doesn't fit can be torture regardless of the brand name or design claims.
HTH
