Give me the mutual attraction with external obstacles over the wear-her-down trope any day! That's the one that I hate the most.
Right?! How can wear-her-down be more appealing to anyone? I mean, there are much better ways to woo someone who isn't interested than by badgering them and guilting them into reciprocating! This is actually a huge part of the appeal of Mr. Darcy. He's upset at first when Elizabeth rejects his super condescending proposal, but then he takes a good long look at himself and puts in the effort to address his major character flaws and rectify past mistakes. Not because he expects her to then fall into his arms—he doesn't even expect to see her again! Similar thing with Harry and Ginny: Harry was never going to fall for the spazzy fangirl who couldn't even speak to him, but he could definitely fall for the funny, feisty athlete who stands up for other kids who get picked on. Angel kind of does this too. When he sees Buffy and realizes what she'll have to go through, it's inspiring enough for him to pick himself up out of the gutter because he's no use to her there. He doesn't do it because he's trying to get her to fall for him. That happens by accident.
Even Han undergoes a lot of character development between "Do you think a princess and a guy like me...?" and "I'm nice men": risking his life to bail Luke out against extremely steep odds in the battle of Yavin IV, risking his life again to rescue Luke on Hoth, and sticking around to help the rebellion in general, despite initially only being in it for the money. People criticize Han and Leia's first kiss, but Leia definitely noticed all of that character development and was just clinging to the last shreds of her initial dislike because it would be embarrassing to admit her feelings before he admitted his. So, basically, the most effective wooing strategy is unassuming character growth.
Which brings us back to the love/hate thing. The key issue, I think, is the nature of the bickering. I actually have some experience with this. There was one boy in high school who would argue politics and religion with me every chance he got (which was a lot, because our last names start with the same letter, so he was almost always seated right next to me when we had assigned seating), frequently mocking and belittling my beliefs and interests. When people speculated that he might have a crush on me, I was revolted. There was another boy who was consistently annoying in more shallow ways, but the second I found out that he liked me, all of my irritation evaporated and, to my surprise, I found myself deeply flattered. (Nothing came of it because my family moved to a different state less than a month later, though.) So, is the bickering over dumb little stuff that doesn't matter? If so, it might be a defense mechanism two very stubborn people are using to guard against their own feelings. Is it over deeply held beliefs? Then the instigator might just be a jerk who takes pleasure in harassing others. Xander and Cordelia conceivably fall into the defense mechanism bickering camp (although it seems a bit borderline), as do Ron/Hermione, Han/Leia, and Beatrice/Benedick. Buffy and Spike are blatantly in the latter camp.
Which brings us back to wear-her-down. I *hate* ships where the guy is all "you know you want it" and will not leave the girl alone, Biff Tannen style. That's why Buffy/Spike is one of my biggest NOTPs (the other is Caroline/Klaus, for almost exactly the same reasons). Sometimes—often, even—, the girl actually doesn't want it at all. Fancy that. Sometimes, she might be a little bit attracted deep down, but so what? Sometimes we like things that are bad for us, and denying ourselves those things does not mean we're lying to ourselves, it means we are wisely exercising self control.
