I have always found it down to personality.
Taffy (nethie cross) is an active bunny, but i have found she is irritated by active rabbits. She was originally paired with my bridge bun Trio who was very disabled. She loved to nurse and care for him. Then she was bonded to Flynn for a spell, but the bond was not good, as they wound each other up. Taffy will bolt and run into her partner looking for a reaction, then have a proper go at them, sounds bizzarre but its true. When we tried to with a rescue boy called Echo, she hated him because he was active. Now she is with Riley (frenchie x EL) who is three legged and bulky. He doesn't do anything fast and would far rather lounge around, so he does not upset her.
Holly (english spot) is bonded to dwarf lop Frodo. Holly is highly strung and easily offended. She likes to be dominant but also likes to do the grooming, so i guess she is happy to kiss a bunny as long as she is being respected. She was bonded to my bridge bun Bigwig (a three legged lionhead). He was happy as she groomed him, and she was happy because he didn't want to hump her :lol:. Now with Frodo, he is very laid back (almost horizontal) so she will happily groom him, in the knowledge he wont annoy her.
Giles (english cross) and Summer (blind dwarf lop) i have no idea. They just fell in love the second they met. Its a funny relationship, most definatly the strongest bond of all my pairs. Summer will run about and bump right into Giles and he doesn't even flinch, he just looks at her, and if he could, he would roll his eyes :roll: :lol:. I have no idea who is the boss or what makes the bond work. It was just love at first sight.
So, i would say, with my buns it is down to personality compatability. I suppose, just like humans, for a bond to truly work it has to go further than looks
. This is just based on my experience.