Prety Much A Matter Of Branding...
Nissens radiators are made in Denmark to exact OEM specifications. The only advantage of the BEHR radiator is the fact that they were factory original. Performance, quality and longevity are about equal, but some people have got better performance out of the Nissens. The main thing to look for is the newer reinforced filler neck on the upper tank. The older plastic ones get brittle and break off, so they have added a metal insert.
I am wordering why you think you need dual fans. Cooler isn't always bettter. Your engine needs to operate at an optimum temperature. Cooling it too much can rob you of power, performance, and fuel mileage.
If you are having cooling system problems, you probably need to do a flush with both the MB degreaser, and citrus cooling system flush. Then just be sure you use the correct mixture of de-mineralized water and Mercedes-Benz brand antifreeze, along with the correct pressure rated radiator cap.
"We drive into the future using only our rearview mirror."
- Marshall McLuhan -
Northern California Wine Country...
"Turbos whistle, grapes wine..."