IMO, BHS are easier skill-wise, but induce more fear. My older daughter prefers BHS or cartwheel. She HATES any kind of walkover - front, back, floor, beam, doesn't matter. She's very strong, but struggles with flexibility (for a gymnast).
Now, when I was a gymnast, I preferred BWO to BHS because I was really flexible so it never hurt and it wasn't as scary to me. I hated cartwheel on the beam, which I didn't do for very long (because it was awful). Or any front/side tumbling because I was NOT a fan of the blind landing thing. I'd rather not see going into it (during back tumbling) than see where I'm going but not where I'm landing (during front tumbling). I'm always impressed with people like Brenna Dowell who are so good at front tumbling, because I was terrible at it.
ETA - I think really good BWOs are rare. Someone on youtube or somewhere just posted a video of a girl qualifying to junior elite (the compulsory beam routine), and that BWO is a thing of beauty. I don't remember the name, but it was gorgeous. Anyway, I know that technically speaking people say that BWO is easier than BHS (and it's that way in the ICOP, an A skill vs B skill), but if you just look at some level 5-8 meets and watch girls do them... the form is almost always better on a BHS than on a BWO.