My head much more often than my heart. Had I followed my beat I'd probably be somewhere entirely else. Not sure if that somewhere else would have been better or not, but it would have been a different me.
I want to say both, but I've come to distrust my gut instincts. Sometimes it fails me miserably. So I think I'd prefer to follow my head first before following the heart.
And also I've seen a lot of people affected around me (including myself) because of what someone did by choosing the heart. I would prefer people think about the consequences of their actions and who they might affect first before making decisions.
Historical, fantasy, magic, horror, supernatural, survival, vampires, demons, pirates, mutants, ghosts, romance (FxF, MxM, MxF) (Romance should be part of the plot and not the whole plot in itself), etc.
I follow my head which is probably why I get so lonely sometimes lol also because my heart will tell me everything is awful. My fight or flight reaction is all mucked up