See, the thing is, I wouldn't want to have sex with either of them. Why is sex so necessary? At the very least, it's a sin against nature. At the very worst, you're going to end up with 1/4 fish babies running around, possibly haunting Innsmouth.
I'd go with the female top-half so I could have somebody to talk to. And, if it came to that, a blowjob wouldn't hurt.