Pros and cons to both.
As CdnoilRAM pointed out, having a fan in front of the rad restricts some of the air flow, so if your cooling system is at near capacity, could case issues. For maximum cooling efficiency, a single fan that is properly sized for your rad will be about the best way to go.
However, 'WHEN' your electric fan quits, the second fan (if you have it) will at least provide you with some cooling, likely enough to get you to where you need to go to get it repaired.
So....pros and cons to both setups. If I were to do this mod, I would do the single fan setup that CdnoilRAM has done......but I would carry a spare fan motor under the back seat.
(I don't do tow trucks!)