my fiance and i just got an x3 and i think the main reason for the decision for the particular model would be fuel conservation (23mpg), ride height of the SAV vs sedan, and extra room, i've never been a fan of the smaller suv's but if anything i think the x3 in particular is more like a crossover than anything else, handles like a heavy sedan with the ground clearance and stability of all wheel drive traction control, maybe it is labled by some as a sorority chick car, better than a soccer mom station wagon, not that i don't drool over the 535xiT at the dealership every time i'm there
