I've been on this forum for a few years now and while these cars are not without their quirks and concerns, the x-drive drivetrain itself appears to be extremely reliable... if I can infer that from the lack of posts about failures and repairs. I'm not worried about mine at all.
Assuming you want AWD for snow/ice, a 328 x-drive with snow tires is an excellent winter choice.
Good luck with your purchase decision.
07 328xi coupe SG/Dakota leather, 6-speed manual, sport/premium/cold
02 325Cic vert AW/Montana leather, 5-speed manual, premium/removable hardtop
93 850Ci Oxford Green/Parchment, auto
71 Buick Riviera, 455 V8 land yacht