Funny you should ask this, as I have both a 2013 X5 and 2013 LR4 in my garage right now. We were looking for SUVs with a third row seat and a step up from a Toyo Sequoia and a Honda Odyssey.
We started with the X5 Premium to replace the Sequoia. I can say its sporty, somewhat comfortable, but tight quarters for a family. As with a typical BMW 3 series or 5 series, the back seat isn't really for adults. The third row seat, I would say is good up to about a eight year old kid.
Gas milage is pretty good, I average about 16mpg, guess I have a bit of a heavy foot. The 6 cyl is powerful and quiet on the highway, it has a nice growl inside when you step on it. But it sounds like a 4 cyl Hyundai if you're outside of it and someone accelerates from a stand still.
The first few months I found annoying rattles under the rear seats and was back to the garage three or four times, each time add some tape and grease the contact points.
Over the summer, taking it up into the Adirondack Mtns on some dirt roads (I would even call them 4X4 roads, just dirt, a few bumps and pot holes), you can tell, it doesn't like being off pavement. In fact, BMW calls it an SAV, not an SUV. Also, in the NY winters, without snow tires, you might want to work from home when it snows. I would say the all wheel drive is more tuned for acceleration than traction.
Then after about five months, major engine malfunction, see my other post for more details. http://www.bimmerfest.com/forums/sho...d.php?t=660533
We replaced our Honda Odyssey, known as the "vanther", with the LR4. We've had it for a few weeks now and really enjoy it. For a hulk, its actually got good pickup, until you need to turn. But again, its not made to ride on rails like a BMW. For the lower version of an LR, compared to the Sport and Range Rover, it is defiitely a step up in comfort and class inside from the X5. We have the thrid row seats, and I can actually fit and ride back there (I'm a 6'), they fold flat into the floor as well.
Through snow it has been great. I have not gone off road myself, but on the test drive the salesman took it through a huge gully beside the road, so I know its got capability.
I can't say much for reliability or gas milage, long term. But in the two fill ups, I have averaged around 15mpg. The V8 is for the most part quiet and smooth, if you punch it it does have a nice growl.
The X5 and LR4 are two different cars.
-In the garage, they're about the same lenght. The LR4 is of course a bit taller. Both smaller than a Sequoia and Odyssey.
-Sporty - BMW is fast, coners without question ansd stops quick. The LR4 is big, but takes off quick, you can feel its size in the corners, but stopping is pretty good.
-Off Road - In my expereince, BMW doesn't handle dirt, or bumpy roads well, especially with run-flats. LR4, its made for off road.
-Comfort - LR4 feels nice to sit in, takes pavement very well, and it quiet and refined. The BMW has hard seats, a tight fit (kind of like a glove) and you feel the road - in your hands and your body as you drive or ride.
-Reliability - I'm disapointed with BMW so far. For $65k, I would expect better. Can't comment on LR4, have not had it that long.
-Tech - I like the BMW iDrive better than the LR4 touch screen to contol functions. The BMW system has gremlins though, settings will not save and go back to default when you turn the car of and get back in. Both have phone integration, iPod integration and wireless streaming. Don't get the BMW internet option, waste of money, its like AOL dial up back in the 1990's.
Good luck, they're both great vehicles and I enjoy driving them. But figure what you're needs are. Hopefully this has helped a little.
If you have any specifics, feel free to ask.