A really great burger starts with quality beef. It should have processed cheese that melts well. And it should be inside of a potato bun.
Don’t give me ciabatta bread for a bun. Don’t give me a kaiser roll. As good as brioche can be, it’s not well-matched to a burger. The bun is a delivery vehicle for the burger. It needs to be big enough to contain the burger, but shouldn’t be so large that it overwhelms the burger.
Everything you put on the burger needs to fit inside of the bun. You don’t want the burger to fall apart when you eat it.