I drive RWD coupe with continental conti pro SSR all seasons here in Colorado. Never been stuck because of the tires.
If the snow is above the side skirts, even the XIs wont get you out of the snow.
Its a preference. If I were to buy a 3 series for my fiancÚ, I'd look for an xi too(in fact I am still looking for one that is not abused).
Not that she is a bad driver, but its an envelope of security for me.
Tires with good tread and taking it slow in the corners with make RWD as good as AWDs. If one drives like a moron, even AWD will get stuck.
If you want a ZHP get one and buy a winter beater for those nasty more than 6" snow days.