Not trying to sound rude, but I'm assuming you've never driven a BMW. Driving quality makes this an easy decision. If you like the cushy, automated japanese style of a ride, go with the Lexus. If you like to be able to hear your engine, enjoy a stiffer suspension, and place a value on German engineering, you need to buy a BMW.

That said, if you like the styling of the new X5, I'm sure it's twice the car of the current X3 (being an X3 owner). I bought an 11-month old, 16,000 mile used X3 for $12,000 lower than the sticker. This would put the new X5 right in your price range next Christmas, no luxury tax, no gas guzzler tax, and a like-new vehicle. Just a thought. . .