Serebii: I haven't ever been to the forums except once, and that was when someone accused me of copying their moveset. I really think its gay when people think that you steal their movesets only because they have it, even though they don't know that you had it before them. I was accused for stealing an SD Heracross moveset from Smogon when theirs was the one that didn't have Facade, and then all of sudden it changes. Other than that, I have never read any threads on Serebii nor have I registered there.
Marriland: Haven't been here at all, unless I'm looking at the PokéDex. Serebii's my first stop when it comes to looking at a PokéDex though, so whatever.
Smogon: I've registered at Smogon, but I don't really read the threads often. Once in a while I'll go rate a team in the RMT section or play on shoddy (not sure if I should associate that with Smogon, but I guess I could).
Friendcodes: I've actually been more active here than any of the other listed sites, but I don't really know too many people here. It isn't a bad place, and it for some bizarre reason I actually started posting more often on this site in the past month or two. I registered in October or something, but Friendcodes happens to be one of the two sites that I visit the most nowadays. The other site I'm referring to... well I can't advertise and I wouldn't want to anyway, but I've been there for more than a year and that's where I developed most of my experience with the D/P Pokémon battling meta game.
If you decided to skip the block of text, this place is smaller, which is why I like it. I don't like my name flying all around and would rather keep my identity a secret / surprise, because when I get beaten someone's going to start bragging and it really ••••es me off. Oh wait, that had nothing to do with the big block of text. I like Friendcodes the most :D Really, not saying that to make you guys happy. Well, out of the options posted Friendcodes is the best. Alright I have to stop.