Only thing conclusive that I’ve read is in the MP engine book regarding horsepower and torque: as it relates to new fans, 6 blades, symmetric, flex and plastic. No mention of cooling performance. Probably safe to say they went with the asymmetrical 5-blade for the best balance of power and cooling? I know I’d rather have a 17” version (I could probably cut a 1/2” off each blade on an 18” version...hmm) than the HEAVY 6-blade Derale I’m using.