The smell hits you before anything else. Beef fat dripping down onto an open flame, catching, and curling back up as smoke through the meat. Anyone who has stood near a flame-broiler knows that smell, and it is the reason two burgers made from the exact same beef can taste like they came from different worlds.
People argue about burgers the way they argue about barbecue. Around Cleveland, TN, where a flame-broiled burger is taken seriously, the question comes up a lot: what is actually different about cooking over fire instead of on a flat griddle? The answer is more interesting than just "one tastes smoky."
What the fire actually does
A griddle is a flat, solid surface. The burger sits in its own rendered fat and cooks in it, which is delicious in its own right. A flame-broiler is the opposite. The grates are open, the heat rises from below, and the fat drips down, hits the flame, and vaporizes back up into the meat. That rising vapor is where the char and the faintly smoky edge come from. It is not added smoke. It is the burger seasoning itself with its own juices.
You also get those dark grill marks, and they are not just for looks. Where the meat presses against hot metal, you get an intense version of the Maillard reaction, the browning that builds hundreds of new savory flavor compounds. The stripes between the marks cook more gently. One patty, two textures.
Why a smash burger tastes so different
Here is the twist. A smashed griddle burger is not worse, it is chasing a completely different flavor. When you press a ball of beef hard onto a screaming hot flat-top, you maximize contact, and you trade some juiciness for crust. Almost the entire surface browns at once, building a deep, crispy, lacy edge and a sticky brown layer of flavor that cooks call fond.
So the real difference is this. Flame-broiling pulls flavor up from underneath with fire and fat, and lets a lot of the grease render away. Griddle-smashing drives flavor down into a hard-seared crust and keeps the burger sitting in its own juices. Neither is the "right" way. They are two honest answers to the same question.
How to taste the difference yourself
Next time you eat a flame-broiled burger, do something deliberate. Take the first bite from the charred edge near a grill mark, then a second bite from the center. The edge will taste deeper, almost roasted. The middle will taste cleaner and beefier. That contrast is the entire point of cooking over flame, and most people eat right past it without noticing.
Pay attention to the drip, too. A flame-broiled patty loses more fat to the fire as it cooks, which is part of why it can taste less greasy and more like beef. It is a small thing the old diners figured out long before anyone was writing about the Maillard reaction on the internet. They just knew that fire made it taste right.
The funny part is that "char" is not really one flavor at all. It is dozens of reactions happening at once, sugars and proteins and smoke, all set off by a little heat in the right place. We just gave the whole experience one short word, the same way we say "home" and mean a hundred things.