There didn't seem to be any correlation with the main form of the dæmon and who the person was. Some characters I would have though would have had creatures considered "strong" had what would otherwise be prey animals. There's even the tale about the person that didn't like water, but became a sailor to be close to their dolphin (?) dæmon.
So as much as I'd like to choose an animal I would like, random chance would likely decide for me.