Every burger has to go on something and traditionally that means a bun.  Bread is out simply because it gets soggy and you can’t handle the burger anymore, and there is no way to eat a burger other than picking it up!  Yes I’ve seen people eat a burger with a knife and fork but we all know that’s just deviant behaviour.
For the ultimate burger experience I like a bun that fits the patty nicely, isn’t too soft as to squish up and doesn’t get soggy and has sesame seeds …