A lot of women have 'classic' feminine faces with a soft chin, that means neither pointy nor a strong jaw. Those two categories really doesn't cover the most typical ones.
I find the pointy chin much more attractive, I think a strong jaw looks way too masculine for a woman. However a strong jaw will typically make you more photogenic, it looks better in photos and on screen for the way it 'captures' the light (same as high, defined cheekbones). Which is why so many models have strong jaws, and as the trend goes, a lot of actresses these days as well. I was watching a movie with Eva Mendes (who has an extreme jaw) with a guy I know and he commented how a lot of actresses look more masculine than their male counterparts these days. I hadn't really thought about it until he mentioned it.
I do think Keira Knightley is pretty, but I think she is attractive in spite of her strong jaw, not because of it. Salma Hayek looks to manly to me. I would much prefer to have Jessica Alba's delicate features.