The answers are not simple. I use fem seeds and I think it depends a lot on the strain and where you get them. Old strains are more stable and less prone to hermie. I use Northern Lights from Nirvana, and have never had one fail to germinate or be female. To me it is well worth a few bucks not to have to cull male plants.
But if I were growing this and that new strain and experimenting, I wouldn't go with fem seeds.