I say they are both very girly tomboys. They are tomboys, but have a bunch of girly features. It seems like Dash is more of a tomboy at first, but as you watch more episodes, you can see that she can go fan girl mode, kissed a para sprite because it was cute, actually requested Rarity make her a dress, and more traits too. So I would say they are both equally feminine and masculine.
Me want some delicious cookies.