One point everyone is missing is the fact our skylines were never designed with thermo fans in mind. Obviously a car which the whole cooling system aerodynamics have been worked around a thermo fan the system will work. Also modern vehicles are becoming more complicated and the engine bay is becoming filled more and more with equipment so obviously the easiest thing to get rid of was the clutch driven fan. That does not mean that one is better then the other.
Also in regards to the v8's/f1 remark. I dont see jetski's with a rocket pack, What's your point? They are in no way street driven cars they are running at high speed 99% of the car vs 30-50% of the time for street driven cars. What also you are missing if you are a mechanic, Is the fact that you are increasing the load on the alternator. This does load the engine up somewhat if you do diagnosis load testing on a vehicle at 100% alt load you will see your engine load % increase. The only reason i could see that you would want to fit thermo fans to a vehicle design for a viscous fan is either appearance or space if you have converted a dfferent engine. Btw im a diesel fitter and nearly every road train/ industrial engine is clutch driven and anything large IE large dump trucks, loaders have a hydraulic motor driving a fan ( talking about 2-3 mtr span)