I swore by the Blizzaks on my 328i which was useless in the snow and needed 3 sand bags in the trunk in addition to the Blizzaks

I have been 100% satisfied with the Dunlop Grandtrek WT M3 that come on the BMW winter wheel package though. The X5 surpasses pretty much any other vehicle with those tires on. I have gone places and been able to go on roads that other SUVs have not.

So I think you'll be happy with pretty much any winter tire...