When the X5 4.4i first came out, the Sport Package included 19" performance tires that were not suitable for driving in the snow. Many people opted for the Sport Package thinking that they could handle bad weather, but ended up being screwed over because they didn't realize what kind of tires were equipped with the car. Now, if you get an X5 4.4i and opt for the Sport Package, they give you 18" all-seasons with sporty-looking wheels, and then there is another "19-inch Performance Wheel Package" where you get the 19" wheels that originally came standard on the X5 4.4i Sport Package.
One time we had a light snowfall and this random X5 4.4i w/19" Sport Package came up my driveway...the snow was very light but I saw the X5 had some wheel slippage getting up. On the way down (after realizing he had the wrong house!), the guy almost crashed into a tree because he was going a bit fast and the tires were just not really getting much traction.
The only thing X3 buyers need to watch out for is the 3.0i. If you are getting an X3 3.0i and you plan to drive in the snow, you can opt for the Sport Package that gives you all-season tires. After the Sport Package, you can then opt for the 18" performance tire/wheel package. Going for the Sport Package is fine, but do NOT opt for this performance/tire wheel package UNLESS you will not be driving in any snow OR you plan to purchase snow tires for the winter months!