Not as much as...? I presume you were going to say Zexion? Going by your avatar, of course.
I think Xigbar is my favourite member of O13. I don't know. I really like Luxord, too. But Xigbar's probably at the top because of his attitude, his accent, his element, his weapons and because--you must admit--he's sooo sexyyy.
As for Axel... Meh. He's okay. I'm not an AkuRoku fangirl. I prefer Xemnas/Saïx. But people would probably murder me for saying that. D: