My cooler is a DeRale 16-pass fan assisted model. It has an integral thermostat and relay to turn the fan on when the oil temp climbs above 180F
The key things in a cooler are:
(1.) The number of passes of the tubing - 9 pass for light applications, 16 pass for more HD cooling. You want more cooling capacity.
(2.) A fan assist to move more air through it, especially when stopped.
(3.) AN8 style connections
(4.) Integral mounting bracket
(5.) Where it is located for optimum airflow and max cooling