It all depends on the drivers. If you have a high current, it's going to build heat. The more heat, the better the heatsink has to be. To give you an example, I have two flashlights that use the same LEDs, and use the same drivers, and same batteries - but one has a smaller heatsink and gets quite hot quickly. The other is larger and never gets hot. Both put out the same amount of light, but the one with the deeper reflector focuses the beam more.