I can't say much for a Nissan 350z because I never test drove it, but I can tell you for sure that the g35 is a bad choice.
It has 280 horsepower which you don't feel, I beat g35's in my 2000 328Ci. The car's handling is nothing like a bmw. There shouldn't be any rear seats in it either since I cant even sit there without twisting my neck to the side and Im only 6'1" not exactly super tall. There is laughable trunk space, there is no full size spare, the only good thing about it is the price. You can get one fully loaded for 24 months under $600/mo. but its definitely not a great ride.
I'd say test drive a few BMW's if you havent, dont let the tech specs on paper fool you, get a feel for the car. Find the car you absolutely love even if its out of your league then get a car that most closely resembles it. In my opinion for the money you wont get a better car than a BMW, and you will have a lot of fun in the snow with RWD. I know I did when we had plenty of snow in NY this winter and I had on summer tires
Anyway, just my opinion.