Fans and cooling

[MellowCharger]

Will twin electric fans cool more efficiently than the standard factory fit item?

I don't like the fact that the twin jobbies have a cowling/surround that blocks the flow of air in parts.

[elacruze]

Heat exchange in the radiator is almost entirely a function of frontal area. The factory shroud exposes 100% of the radiator's frontal area to moving air at all times. Electric fans without shrouds only pass air over the radiator area they cover when stationary, but allow road speed air to pass through the entire radiator. Electric fans with shrouds will pull air through the entire shroud area, but my personal opinion is that if they are mounted close to the radiator they don't allow enough plenum for the road speed air to move through and exhaust.
I'm sticking with the factory fan because it works well and I already have it, and I plan long trips where I may have to rely on auto parts stores for repairs away from home.