It's all about wheel width size and tires.

I once ran Bridgestone Blizzak WSxx on a rear wheel drive sports coupe for a winter and took the car out in the middle of a storm (I was young, stupid and curious, lol) after a foot had already fallen and had no problem (except having to pull over to clear the snow out of the air intakes on occasion...!) where some SUVs were getting stuck.

In my humble opinion, the right dedicated winter snow tires and a narrower wheel width should get you excellent traction in snow in the X5. I run Continental DWSs on my 4.8is with factory OEM rims and get pretty decent snow traction, driving with some basic common sense -- and that's just an all-season tire.