I could be friends with either Faith or Buffy, but neither one would happen without some outside circumstances pushing us together. There's as much "distance" between me and Faith as there is me and Buffy. (Though don't get me wrong, I enjoy the show a lot. I also enjoyed Faith as a character with me getting to like Faith more than Buffy in season 7, though I liked Buffy more before 7.)
But if you mean who do I think is the most pleasant on my eyes then I'd go with Willow. I also prefer Buffy's fashion to Faith's (but my own fashion isn't like either one).
Willow is face pretty but has no hips. That the character acts like a sociopathic spoiled child does not make her attractive to me.
Buffy, Faith and adult Dawn are all nicely curvy though Buffy is too thin in some seasons. I like fit, curvy women. Cordelia is hot, esp in Angel season 1 and Buffy season 1 (those green painted on pants)
Also attractive: Joyce, later Tara, Dru when not in vamp face. Her vamp face is very reptilian... It creeps me out more than nearly all other vamps.
Anya is fun but physically; mostly too many angles.
I always thought Oz (the man) was hot. He was a pistol. Seriously muscular and tight bod. I like this in a man. He made a very good were... He moved like a wild animal... And that is a compliment. I am not height obsessed unless they are noticeably shorter than me 5'6". Yes, I find Spike very attractive except for his (fake?) chin. Body is smoking.
Ethan is hot, but i always find his character reads as gay (he and Giles are sooo hot together!) so i tend to not look as hard bc my brain says "not available"... But objectively i find Robin Sachs very hot.
I don't like beefy men so neither Riley nor Angel have any physical appeal. Blucas actually makes my skin crawl, not just in Buffy. I actually like Angel the character, particularly in his own show when DB learned to act and not just drift sexily from scene to scene.
Special mention: Principal Wood. Oh my. Man is a stiffner... (To quote Doyle)
The only other large men on the show i find attractive are Giles (he is magnetic, smart and can sing) and Graham Miller, who would have made a much more interesting boyfriend for Buffy IMO (Bailey Chase also seems to be a better actor, especially back in the Buffy era)
** My favourites** Probably Buffy. There is a lot of competition. Faith and Cordelia would be runners up, mostly losing for facial expressions that make them look hard and/or mean.
*NOTE: Not including Angel only characters.