let's jsut remember this: most bmw's have perfect 50/50 weight distribution. and if you're spinning wheels in the snow, you're either a)not good at driving in the snow, or b)asking your car to do something it's not made to do. However, if you get a second set of rims & tires designed for the winter months, with dedicated studded winter tires, you should find that with some cautious driving, your z4 will be fine. Oh, and get a manual, you'll like it better if you drive for performance in the summer. as for all-wheel drive, it's a personal preference, b/c once u really learn how to drive fast, all-wheel drive gets a little tight on dry pavement once you're used to real-wheel drive. finally, the x5 is probably the only suv you would enjoy after owning another bmw, however in the summer months you're gunna wonder what it would've been like to own a z4. I just went from a chevy silverado to a 328i convertible (e36) and haven't looked back!!