Living in the snow belt in the US (and owning rwd and Xdrive over the years) I'll weigh in with this:
RWD with snows is better than AWD with All Seasons
AWD with Snows is better than RWD with Snows
I do not believe AWD is a "significant" gas mileage penalty
OP, if you love the driving experience the RWD gives you, gotta have a MT and live where it's snow and or cold? Get some snows, get rwd and have a blast.
For me? Xdrive all the way...Glad we have choices
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Previous Rides: 535xi, M235xi, X3, E92 M3, E70 X5 35d, X6 50i, X6 35i, E60 550i, E46 M3 Cabriolet, E39 540i, E36 328i