None of them. Unless you like your characters to look like porcelain dolls with anime eyes or have a fetish for furries.
Seriously though, I personally write my own mods. It takes little to no programming knowledge, at least I don't think it does... The developer offers up the tool to do it and it's pretty darn cool to use. Unfortunately, no matter how much you mess with the heads they almost always look the same because of the facial texture in use. You can't change that even with a mod without affecting all the NPCs in the game.
I've experimented with community mods for this and also FO3 and in all honesty I can't really recommend anything over the vanilla install. Oblivion was a different matter, but not this game. Others will disagree