I owned a 2007 MDX for a year. While I liked it, I thought it was much more sluggish overall than the 3.0 X5 (even though the MDX specs are better).

I agree with another poster here, the MDX ride is just OK, it felt heavier and choppier. The MDX is a nice SUV, but seems to me to be more like a really nice Honda than a true luxury vehicle.

I just took the X5 on a 4000 mile trip. It is much more responsive a higher speeds than the MDX was.