I pulled the set of fans (John's) off my car and his shroud is only 3/4" shorter than the OEM shroud. So the EU radiator is longer than the OEM unit. But John's shroud has a very sharp slope on the outer edge and the center where the two shrouds are welded together would also block air flow. John's shroud is very thin (a few inches less than OEM). He even had to grind the nut that holds the fan blade onto the motor shaft to clear the radiator. This means his fan blade is very close to the radiator. My guess would be only the area of the fan blades is where you get air flow through the radiator.

Someone would need to do a cooling test "BTU" to really compare effectivity. I must say when running John's fans, my engine temp would only go up when I was in the mountains climbing a long hill.