For vehicles with electric OEM fans that were designed and developed by the auto manufactureer, they're great. As noted aftermarket systems or adapting a OEM fan to a different vehicle leave a lot to be desired in reliability and cooling capacity. OEM fan systems are engineered for the particular vehicle and it's use.
My 1st gen Vortecs have never had a cooling problem even on hot days at altitude--where the thinner air does not carry heat away nearly as effeciently. I installed a factory style HD radiator in my 96 K1500 when the original began leaking. I can't hardly budge the temp gauge off of 190-195 on a hot day with the a/c on when blasting up the pass with a load of camp/hunt/mtn bike gear in third gear at 3k + rpms.....
My 91 Light Duty K2500 with a 5.7, NV3500, 3.73 gears came with the smaller radiator of that era. Pulling a trailer on a hot day with the a/c on even a moderate hill would make the temp gauge climb and it wouldn't stop climbing until I shut off the a/c. The radiator was undersized for the application. I beleive it was 93 or 94 when GM went to the larger radiator for the GMT400's. The dingbats should have done that to begin with.....
My observation is the hot rod aftermarker (expensive) aluminum radiators are not as effective as the OEM style normal or HD radiators.
And I've given up on HD fan clutches. As noted they're engaged when they don't need to be, and most roar like a 747 on takeoff, and most likely are sucking more power and gasoline than they are actually cooling the motor/trans. After several HD fan clutches I installed a AC Delco "normal" fan clutch on my 96 and me and the truck are happier about it.