if you are looking for a vehicle with the space and utility of an SUV but still want close to M level driving experience, the 4.6is / 4.8is is the best option in the market. If you think X5's are expensive to maintain, you should take a look at what it costs to own a Cayenne S or Turbo. About the only other vehicle in this category is the E55 wagon, which is uber-rare and RWD - so if all you need is cargo space and not the AWD capability or towing ability, it may be an option. I need the AWD and the cargo space, and I have the occasional towing need. So the X5 fits the bill very nicely. And the 4.6is is a very nice driving vehicle. I have owned a 330i, 540iT, an E36 M3 and a E39 M5 - all of them special cars in their own right and no question the type of cars that BMW does best. But the X5 in "is" form is pretty damn nice too and well within the spirit of the BMW cars I have owned. the "is" is much better than a 3.0 or 4.4i, IMHO.

To the OP's question - if you can afford the 4.8is, I would get the newer model for sure. I got the 4.6is because it was all I could afford for the slot in my garage I was looking to fill. I am very happy with it and no regrets. But if this is your primary car and you can afford it, why not get the newer one? :dunno:

Depends on what you want out of it....

The 4.8is is a bit more refined in driving experience and has a few more options like x-drive, pano roof, valvetronic, 6 speed auto gearbox, 4 wheel air ride etc. But is not as powerful a driving experience as the 4.6is.

The 4.6is has the same HP as the 4.8is, but with MORE TORQUE! Has the M62tu retouched by ALPINA, who balanced the crank and ported/polished the heads etc. thus making the engine internals more reliable. Has a beefed up version of the 5 speed auto which is less problematic than the 6 speed. Has the smaller sunroof, which is less problematic than the pano roof. Has the standard transfer case, about equally problematic as the x-drive case, but with less parts to wear. Without the valvetronic, which can be problematic. only rear wheel air ride (self leveling), which is one less axle to worry about. (air struts can be expensive) Etc.

Don't get me wrong, the 4.8is is a BEAST and offers a driving experience that needs to be felt to appreciate, but the 4.6is is slightly more beastly, has more of a raw power feel when driving, less expensive parts/systems to break. And don't forget..... you can supercharge a 4.6is, but not the 4.8is.

But I reiterate... it is your decision to make as only you truly know what you want/need out of it.

(ps, notice people with the 4.8is recommend it while people with the 4.6is recommend it? funny huh!)

well - I recommended the 4.8is but only on the basis it is a newer model. Although sometimes that is not better. For example - I would take a E38 over a the newer bangelized 7 series any day!! But I digress.....

Weasel makes some good points. I have not driven a 4.8is, so I cannot compare. I did drive a 4.4i both pre and post facelift and neither compared to the 4.6is in any way shape or form in terms of driving excitement.

Good points.
I bought 4.6is 4 years a go because couldn't reason myself spending $20k more for a truck with similar mileage with only 2 year difference in age.
Now, when price difference is not as much I would probably buy the 4.8is, as it has better enginge, more power, more torque and better transmission.
What comes to xDrive difference, probably 95% of the people don't even need the 4-wheel drive, i.e. occasional driving to Cottage or winter driving on main roads, the old xDrive or whatever it is called does the job, I've driven 3 winters without problems now.

Sorry, Weasel. 4.8is is more powerful and more HP than 4.8is. ;) :)

Screen shots from the respective manual as below:

X5 4.6is - 340 HP 350 torque
X5 4.8is - 355 HP 369 torque

My mistake Lemans, I was working off of a different source for specs and didn't notice the torque specs said NM by it... oops!

But as a person who has driven both models numerous times I can objectively say that I prefer the 4.6is over the 4.8is for the reasons of driving feel. I prefer the more raw feeling and quicker to respond torque, more resilient to wear block/rotating assembly, less likely to have wear/problems valve train etc. of the M62tu. And I prefer the feel of the beefed up 5 speed tranny with more aggressive programming than the softer feel (except when it is having "harsh shifts") 6 speed.

(PDF source below)