We have both a MDX and X3. I have a friend who is dumping their X5 due to repair costs .....$3,000 for a sensor? We purchased the X3 as a CPO and was underwhelmed when we had a warranty issue and the dealer told us not to drive the car until we could get in 6 weeks later. Needless to say, after calling the dealership GM, the car was fixed in 6 hours. Normal things like a battery are $500 due to programming. The radiator failed at 60k. As we bought this well ($$), don't drive it much (5k), it is not an issue. But the minute the X3 becomes problematic, it will be replaced. BMW's are great until something breaks. Another friend is replacing his BMW X3 because it needs $7500 worth of repairs at 130k. He bought a Subaru.
The MDX is my eighth Honda product. In every case, we've gotten over 200,000 miles out of them with minimal repairs. They are less expensive to repair and maintain than a BMW, don't break down as much as the German cars. And the parts are much more available.