This fan looks suspiciously like those supplied with external oil coolers, which would also lead me to believe that it is drawing air into the engine compartment.
In terms of increased efficiency for sucking versus blowing and similar performance for both; in general this is true (think engine driven fans with conventional untipped blades), but almost always fans in automotive applications are designed to operate in one direction only, and therefore have increased airflow in one direction.
The fan blades are a "forward skew" design (meaning that the tip of the blade is forward of the blade root on the hub) which is a more efficient blade than a "backward skew" blade (which is the opposite). the band around the edge of the fan is there to not only add structure to an otherwise thin blade, but also (when combined with the right fan shroud design) can have a significant effect on performance.
The "cupping" of the blades is in fact a means of reducing the weight of the fan, and has no real effect on the efficiency, but would affect the fan performance were its direction to be reversed.
The only thing I would change is to fill back in all the open space around the outside, because all you're doing otherwise is recirculating air around the fan.
I wonder how it is controlled? Is there a thermostat somewhere? How would you calibrate between cylinder head temperature or oil temp and the ambinet temperature in the underhood environment?
Stan, you mentioned that you "do fans" to support your speedster habit, are these automotive fans? That's what I do to feed my obsession.
Cheers,
Jim.