I don't know why everyone keeps implying that Faith was weaker, or a worse fighter? I seem to recall that whenever Buffy and Faith duked it out, Faith either had a death wish, (aka letting Buffy stab her and saying "you did it B, you killed me" just as ONE example) or she was going easy because she was going to be in Buffy's body, or, she had an emotional meltdown, or she was interrupted by a third party trying to kill them both (Gwendolyn Post). There was always a motive with Faith, I don't remember her ever just fighting with Buffy, she always had a goal, and though her plans didn't work out most of the time, she never, that I recall, lost to Buffy outright.
It always took some major mental or emotional flip for Faith to lose to Buffy. I'd have to re-watch all of the Faith episodes to be sure, and correct me if I'm wrong please, but like I said, I just don't see where anywhere in the show it was obvious that Faith was somehow a substandard fighter. Plus I don't recall Faith ever actually wanting to kill Buffy. Hurt yes, but not kill, even when she was listening to the Mayor. She was going for the hurt, trying to show Buffy how it felt to be her, how Buffy made her feel. It was obvious that when Faith felt emotional pain she could only express it through physical pain, or violence.
Anyways I always thought Buffy got way to much credit for everything she did. Yes she lost her mother, it was terribly sad, I always liked Joyce, but Faith lost her only real mother figure, her watcher, to a vampire early on. Faith didn't have anyone else when her watcher was taken, Buffy had her friends, Giles, and her sister, and Spike, and Angel. Yet Faith is expected to just get over it, and move on, but Buffy gets to milk it for the rest of the show. Not that I dislike Buffy, I just see Buffy's scarifies blown into huge proportions, and Faiths scarifies ignored. Buffy get's praised for just being alive, or around, who cares if she's doing it well, and Faith get's punished for not being perfect. It's a horrible double standard, and it's truly Faith's loss.
Not that I am excusing all of Faith behavior, because I am not. I am just saying Faith and Buffy were held to different standards.
Everyone keeps saying how faith murdered and liked it.. Are you forgetting that her first murder wasn't a murder, but an accident!?!? if Buffy hadn't instantly turned on Faith in the alley when it happened, if Buffy had thought to help Faith and not condemn her, Faith may have overcame it, turned herself in with some encouragement, and support, but instead, it was "Look what you did you psyco!" No Buffy did not actually say that, but she implied it with everything she did from the alley on. Buffy always acted like it was a murder, not an accident, saying "you killed a man!" not "it was a horrible accident, but you have to take responsibility" not to mention, Buffy wasn't offering to turn herself in with Faith, Buffy didn't acknowledge her fault in the incident at all. If Buffy had said, "lets both go in, let's do this together, it was an accident we will figure this out." I am almost positive Faith's trip to the dark side would have been avoided. There may have been some jealousy issues to be dealt with later, but nothing that would have pushed Faith over the edge like that.
These are just opinions though, and I like I said, I don't hate Buffy or anything, I just see Faith as a more tragic figure, and Buffy as a more overrated figure.