After testing with lots of cooling fans, the top two that I have tested are:
*Yeah Racing 30x30mm
*LRP Esc 25x25mm
Those who are using Hobbywing and 3Racing fans, do yourself a favor, it is only dead weight, it does not cool anything.
I'll be receiving in a few days the Seis Fans and Yeah Racing's 25x25 to see how they match up against each other.
I'm testing these fans using the scale method (Like Yeah Racing's videos) and an anemometer.
Other fans that have been tested:
-Muchmoore High RPM fan 30x30
-R1 Wurkz 40mm fan