I have tried both brands on my car.
The Nittos will waaay outlast the BFG's. Dont even bother driving in the wet stuff with BFGs either. I drove the car daily with Nittos, rain and all, and they lasted at least 2-3 times as long. I think the difference in traction is small, if any between them. Nittos just need more heat to stick, thats all. The BFGs actually start out with a lot less tread than Nittos. Granted I am running 16"ers, and some are running wide 15"s, so I am not sure about those.
...Just my experience. Ask NOSJohnWE4... Hes a dealer for both, and can tell you a lot about the tires.