At least the mermaid can provide a good conversation. The reverse one always wants to talk about plankton (I mean I love a good plankton debate now and then but not all the time).
I think it's supposed to be if you were on a deserted island which would you want as a companion?...I think. And I choose the regular mermaid/merman, because I'd like to talk to someone that didn't creep me out (and the reverse one kinda scares me).