Considering the augmentation process, I don't think it matters if you start with men or women-- by the end they'd look pretty much the same thanks to the ridiculous amount of steroids and hormones pumped through them, combined with whatever else they did. I think they mention in the books how you can't really tell them apart (With the armor on, at least. That implies to me that their basic body shape (hips/shoulder proportions, overall shape, etc.) is the same.

I haven't seen the anime yet but somehow I imagine they prettied up the female spartans. Am I correct?