Looking at stock fan blades, there is no Foil, no thickness distribution, just bent and angled metal designed to pull and push air. it works, it is effective, yet it is hardly an Ideal method for moving air efficiently.
To say it would be ideal, would be akin to saying airplane wings could just be flat. Same thickness front to back with no foil, no shape, all they need to do is be angled upwards to give enough lift to keep the plane aloft.
Now is it worth the effort to engineer a fan blade with thickness flow, like an Airplane wing?
Well, they likely could get more airflow for less noise and power consumed, but it would be a lot of work, perhaps too much mass.
Enter the electric plastic bladed fan. The impeller blades on many are not simply angled, they have foils, thickness flow, and perhaps even a skythe style shape, to better grab onto the air, and either pull it through or push it through the resistance of the alternator, AC condenser, transmission cooler and then across the engine.
So which is more effective?
Well which could be much more effective, no doubt the well designed electrical fan with a tight fitting shroud so all the fans flow is sucked through or pushed through the radiator.
I am a Fan enthusiast. Look at the engineering which goes into some Computer Fans, Like Noctua's latest 120MM fan.
Look at all the little enhancements, like the 'flow aceleration channels' or stepped inlet design to make laminar flow into turbulent flow so the blades can grab more air effectively. Then there is the ultra tight fan tip to shroud clearance, or the inner surface microstructures, and the very mounting designed to cushion the whole thing in soft silicone to limit noise and vibration transmission.
This particualr fan is designed for both good airflow with little to no restriction, and also be quite effective when it is forcing air through a restriction, a pusher style fan. They have fans designed more for one or the other.
Do the radiator electric fans employ any design similarities as these Noctua's, I can't really say, I've yet to fondle one.
I do think the whole automotive engine fan design could be vasty improved upon.
With the computer fan comparison, I have many such fans. Some of them consume 2x as much electricity to move the same amount of air, with no restriction and 1/4 the air if there is a restriction and this is all accomplishe with better electric motor design and the shape of the fan blades. Surely there is a lot of cross over.
Each 25 amps an alternator has to make is said to consume 1 HP from the engine, so a high power electric fan told to be spinning fast, is still putting a load on the engine. As much as a metal fan attached to water pump through a viscous coupling? Likely not.
I've not really read good things about electric radiator fan longevity, which is one reason I have not pursued adding one, and I am also bit of an impeller design snob.
Moving air might be fine and dandy with an angled flat plans spinning on an axis, but I want a nicely shaped foil with an outline designed either to scavenge air in a puller scenario, or push it against resistance, and I do not think anyone has bothered refining designs to have excellent airflow characteristics for lesser amperage consumption at lesser RPMS and making less noise in the process. i think they just rely on availability of sheer RPM, and heck with efficiency of design.
So if it seems little more advanced than the stock flat metal angle bladed metal fan, devoid of an airfoil, I'll leave it stock. for now.