Here is some more theory for you.

I think the problem with the stock fan is that you are always turning the pully as well as the added drag on the engine. The electric fan is going to draw power from the alt and may increase drag that way (not sure about that one) but overall you have removed a hinderance directly from your engine and that means more available power. However, how much power may not be noticeable (could only be like 1-2hp). I'd like to see a dyno test on this.

Here's one that I'm sure isn't too thought of in this arguement, but I like the idea that you can turn the electric one off when hitting water which you can't with the stock one. I'm sure pushing water is real hard on the clutch etc. as apposed to pushing air.