It seems to me that sexy & slutty is relative. After all, these are stories about sex, and for the most part the characters in them are going to be less inhibited and more promiscuous than people in real life. That having been said, what I like to see most in female characters is depth. I’m much more interested if she has a bit of backstory, identifiable mannerisms, believable motivations, and things which are memorable about her besides her cup size. The more real she is, the more rewarding it is to read the story, and the more erotic it is when she indulges in sex. (Which is not to say that I like stories about real women, like celebrities and such; it feels invasive somehow.) Looking back on what I’ve written and enjoyed reading, I seem to be drawn to female characters who are strong-willed, outspoken, just a little impulsive, and bisexual. Of course, that last bit isn’t exactly a personality trait, but it’s still something I like!