I personally think that coed (men and women together) is better. More like a real life.
The idea of only women college, is that women get chance to open themselves without male influence. For example, it is a known fact that some women do not participate in the class discussion and seminars, because they are too shy to sound stupid infront of men. Women college gets rid of such obstacles for women.
However, there are other minuses. For example, there is lack of communication with people of other gender. That's why when i graduated from college and moved to a normal, bi-gender environment, i was feeling a bit uncomfortable when i had to communicate with men.
But don't get it wrong, it is not that we, students of this female college, have not seen men. We had another coed college - Haverford - nearby. And both male and female students from this college could take classes in our college, as we could take classes in that college too. There were also a lot of male professors and male staff on campus. So, it was not too artificial environment as you might think. There is nothing to be afraid of - that's for sure:).