In the thread on URC he (Jang) claims the Castle temps can't be compared to the others because of the fins on the can. But to me it seems possible that the Castle is simply higher quality and more efficient. The lower temps could just as well be from producing less heat to begin with, not dissipating more. I base this off of Patrick's explanation of motor efficiency, lamination thickness, etc. found here:
http://www.rc-monster.com/forum/show...13&postcount=4
To really see what is causing the difference in temps we would need to know the no-load current and lamination thickness of the Leopard/Tacon motors. But I suspect they use thicker laminations and have higher no-load current.
"It all comes down to this: It's expensive to make a good quality motor. And, you get what you pay for." - Pdelcast