Okay. I want to start by saying that while I love love love Kennedy and if she was real, she'd be the girl I would be totally crushing head-over-heels on (actually she's fiction and I am anyway... XD), I prefer Tillow (barely). However, I do like Killow, and I'm going to sort of play the devil's advocate here.
While Tara and Willow is a beautiful thing, there are a few reasons I find Kennedy and Willow better.
1. Some people are attracted to take-charge, aka, bossy. While Willow is completely kick-butt, you have to remember that she's not always the one who's going to step up and take charge. In her relationship with Tara, the two were truly partners because of this, they were content with following and helping the rest of the scoobies, but sometimes they would each have their leader moments.
Kennedy, on the other hand, was a leader all the time. If you could put your personal feelings for her aside, you know she'd be the girl you'd turn to if you needed someone to get things done. She is totally bossy- and with this bossy comes an amazing confidence, someone you want to turn to because they seem like they always know what to do.
2. The pure imperfection of it. Has anyone else remembered that opposites attract? Tara and Willow are both witches, they are both very sweet and helpful, they are both into the same things, smile at the same things, love the same things. They are familiar territory.
Kennedy and Willow are so different. They are exotic to each other. Willow, to Kennedy, is a girl with inner darkness (and we see Kennedy romanticize this darkness throughout her relationship with Willow, making it almost into what Bella sees in Edward, if you know what I mean). She sees a sweetness and a strength. Willow sees in Kennedy confidence, bravery, and that sexy bossiness again. She is fascinated with Kennedy, and that's why the two will never get bored with each other.
3. This kind of goes back to number one, but Killow gives Will the chance to play the more traditional "woman" role (I feel like I'm labeling here, but I don't know how else to say it). In Tillow, Willow is very slightly dominant it seems. While they seem to be partners, little things suggest that Willow is in the higher position. I'm currently thinking of one of my personal favorite lines:
"I am, you know?"
"What?"
"Yours."
That is when I feel not only a lot of tingles, cause that's totally cute, but also I feel like that establishes Willow's position as the stronger one. It also reinforces my point- sometimes it feels nice to "belong" to someone.
Kennedy takes charge immediately, first being the one to pursue the relationship, and then being the one to take charge of it. This doesn't mean she treats Willow as an inferior- it means she gives Willow a chance to be "little" again. I don't think anyone can say that there has never been a time when they haven't wanted to be taken care of like they were when they were little again. I believe that's what Willow felt- she needed comfort from her relationship with Tara. Kennedy allowed her to be a child again, Kennedy took care of her and held her, comforted her.
4. Physical attraction. I think Tara is GORGEOUS. But Kennedy may be more of Willow's type (she is pretty darn hot...). Even if not physically- Willow could totally prefer blondes, but she could love how Kennedy laughs, or the way she turns around, all sorts of little things.
Okay, there's my long, rambling case for Killow so you guys have something to argue with now... 🙂