[BrianG]

IMO, all high power ESC need a heatsink. You can generally increase efficiency by using faster switching FETs. The heat comes from mostly the relatively small duration of time when the signal switches from on to off (and vice versa).

If you look at the output motor square wave pulses very carefully on a storage o-scope and zoom in, you would see that the square waves have a steep ramp up and down, but they are not perfectly straight. This ramp is where the power loss is. So, as long as switching speeds remain less than perfect, there should always be a heatsink to get rid of this excess heat.

An exception would be if there was a way to design the ESC where it could be filled with some type of epoxy-like material that is electrically insulative but thermally conductive. This would spread the heat out to the casing. But the casing should still be metal somewhere.

I still think they should at least supply a metal "slab" so the ESC is still small, but leaves the decision to add a sink to the user.