Originally Posted by Weasel

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!)