I've received good build quality parts from both Racetronix & Caspers.
Regarding terminals that are "crimped and soldered" vs "crimped" -- while soldering is a nice touch, a properly crimped connector using production-like machinery (not hand tools) will provide nearly a "gas-tight" crimp, ie the crimp is so tight that water will not penetrate and the crimp remains electrically sound.
All factory automobiles I'm aware of, rely primarily on crimp-only (not crimp + solder).
Regarding the design of the Casper & Racetronix dual fan harnesses, i think there is 1 key difference. I could be wrong, so if vendors want to correct me , pls do!
Caspers harness: both fans operate at high speed only, from the ECM's "low fan" signal. ie, both fans are either "off" OR run at high speed. This is how Ramchargers originally sold the fan.
Racetronix harness: both fans operate at low OR high speed. Low speed is triggered from the ECM's "low fan" signal. High speed is triggered from the car's own high-speed fan relay.
With both vendors, the car's original relays only provide the triggering signal, and do not conduct the dual fan's high current demand.