A few things decide the brightness of a given LED. Angle of the mounting can be 20* or 50* etc., this changes the direction of the light output, like a flashlight you twist to make the beam wider or smaller. They also use lenses to focus light from the LED's for a more directional beam. And you have the K factor to consider also, the yellow to white range of the light color. This is why you can have the same lamp type producing a wide range of outputs, may not seem bright in one application, but amazingly bright in another.