Most clutched fans can cool better, it was the intent of their design and was intended for use in cars with A/C. They were designed for cars with air conditioning to be able to pull more air through the radiator and A/C condenser. The clutch is thermally activated- the hotter it gets, the faster it allows the fan to spin and the more engine power it requires. When it cools off it will slow down (such as at highway speed when air in front of the car is pushed through the radiator) and use less power. Most clutched fans have 5 or more blades to make them very effective at low engine speeds.
With a solid fan, it spins one speed- the engine speed, and has a linear power draw. It is simple and it works, but is not as efficient overall.
It's fine for any car that doesn't have A/C.
Electric fans are most efficient overall- on when you need it, off when you don't. But if the motor or thermal switch die, you are screwed. But that doesn't happen very often.
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