I can only speak to the M62. I bought my 4.6 almost 2 years ago with 133k has 140k now. Obviously not my daily but I work on this more than I do my jeep that I drive every day. Truthfully, a reliable secondary vehicle isn't a BMW or LR, if you want that get a Toyota, honda.

You will almost have to fix stuff right off the bat. I've had to replace battery, tires, coils, valve cover gaskets, tranny service, spark plugs and a bunch of other random things. I will eventually do timing chain, tranny rebuild and t case if I decided to keep it. hint hint I know someone selling one....

Issues
M62 timing chain guides

N62 Valve stems

Pick your poison, I'd rather deal with a M62 personally.

Both can and will have tranny issues.

00-03 can also have issues with the transfer case. Don't think 04+ had the same problem.

Yes, the 4.4 was used in LR and other parts as well big difference is the Brits sucks at electronics.

What I will say is the thing is a BLAST to drive. As much as it will piss me off sometimes the torque is fn addicting. I knew going into X ownership it would be a labor of love or deep pockets. I think as you are prepared to tackle the big issues, either DIY or paying ALOT, I'd look for something else.

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Current garage:
'03 4.6is Proud X5 Peasant
'93 Jeep Cherokee (XJ)
'07 Jeep Liberty (KJ)
'88 Jeep Comanche (MJ)