For over a year printing PLA only on stock 2020, I've gotten dynamite results with this one:
Positive(s): this fan duct is super simple to print and install. Only parts required is replacing the two fan mounting bolts with slightly longer ones. No need to buy additional fan, or deal with additional wiring. Cheap solution! Couldn't be easier.
Negative: not good if you are looking to print other plastics like ABS -- no direct way to independently control and avoid blowing cool air on plastic being printed (other than physically blocking the lower duct -- i.e. with tape).