Would you rather bang a reverse mermaid or a reverse centaur?

The creature would be a woman sized fish/medium sized horse from the waist up. This includes the brain and all thought processes. The reverse mermaid would have to breathe water somehow and the reverse centaur would be wearing iron horse shoes on its hand-hooves.
For issues of consent, let?s say this creature was your girlfriend/boyfriend 10 seconds earlier and completely consented to everything beforehand.
You have to pick one in order to return your partner to human form, which one do you pick and what issues do you need to work around to get the job done


Source.