I don't really have a favorite character, except maybe Celise.. but that's only because she's a "I'm here for you no matter what!" sort, which it's always nice to have at least one of those sorts on a grand adventure, even if they're not particularly the most interesting personality.
I never feel bad using her. She wants it, she doesn't need it, the ship's replicator can take care of her needs, but she makes a point of indicating that it's her desire. She wants to be used as someone you just sort of collapse into to let the stresses and pains of the day melt away and that's why she's probably my favorite. No expectations, no need for pillow talk, just whatever you desire when you desire it without any sort of moral issue behind it. There's no "god, am I doing this to this person? Am I turning them into some sort of sexual stress ball in contrary to the person they were when we first met?" Simply put, she's about the only companion-character that you don't have to really worry about at all and that's what makes me like her so much. No addiction to cure, no emotional baggage, no broken homes, weird accidents, or other crazy things. Amusingly, she's just a really solid character personality wise.
Nah, no worrying about that, hell she's probably one of the strongest people aboard your ship, if she didn't want something she'd likely make you immediately aware of her displeasure. She has tons of power and ability to do all sorts of things but she's outright happy just pleasing and pleasuring you and any of your friends. There's a very mature sort of energy behind her, pun not intended, bubbly personality. She's pretty great as a person.
As far as hate or dislike?
I don't really hate any characters but I do dislike certain personality traits of some characters. Such as characters that don't give others a fair shake whether it's you or some NPC, characters are written to be somehow better and stronger than you despite the fact you would absolutely wreck their face in actual combat. The sort of characters that seem to make your character hold the idiot ball every time they're around for no discernable in-lore reason just because they're simply written that way. Especially characters who are supposed to be "big and strong" and yet you're both bigger and stronger and still end up acting somehow intimidated and lesser.
A few characters in this do this to varying extents. It's a bit like CoC's Kelt situation, you wonder where all of the willpower, common sense, and intelligence you've made your character exhibit up until now has gone. I mean, really. Can't take someone being an asshole in order to better your skills without becoming a subby slut? Come on. It's made even worse in this game by the fact that "Willpower" is an actual core stat. Yet that's a whole -other- rant in concerns to how stats don't often influence in-game non-combat events in a positive manner.. I mean, they do, just not quite as often as would be sensible, imo.
Of course, you can always just not interact with these characters, which is generally what I do, so that's probably why I'm more slightly negative and mostly ambivalent toward them than outright disliking of them.