I've had clutch fans on numerous classic vehicles. My '66 F100 with a 7 blade clutch fan and shroud from a 70's Ford truck along with a 3 row Modine "Desert Cooler" brass and copper radiator, would overheat in the summer. City driving in the Phoenix heat was just too much. It couldn't cool down at traffic stops. The clutch fan was never running at 100%. The only thing close to running 100% was a HD clutch fan that was louder than heck.
I installed a Chrysler 300C dual electric fan on it and no more overheating. Instantly cured.
I went through the same with my Fox Body. When I installed the 347, I could not keep it cool. I couldn't run the a/c. Once I installed the Contour fans, all was great.
When Ron Davis builds a custom radiator for hot rods that can't stay cool in the Phoenix heat, he installs Maradyne electric fans. Depending on the year of the classic vehicle, they came from the factory with either a mechanical fan or clutch fan.
There is no doubt that properly set up electric fans outperform clutch fans on our cars.
I'll add to this. Electric fans on newer cars shut off at highway speeds unless the a/c is on. Why is that? The spinning fan actually blocks much of the incoming air through the radiator at highway speeds.
In cooler climates than Phoenix and Vegas, one might get away with a clutch fan. The application also dictates what works.
This reminds me of the old beliefs that:
A cooler thermostat makes the engine run cooler.
You need to slow the coolant flow down so it sits in the radiator longer.
"My car runs at 180° all of the time" as if the engine will melt if it hits one degree higher.