Basically these are an up market 80 series Toyota Landcruiser.
Here in Australia the 80 series has proven a very rubust and reliable 4wd. Actually it is probably the most reliable. Even better than its replacement, the 100 series.
If you want fuel economy the diesel has proven the best. It has less power, but its power is in the lower rev range so you dont have to rev the guts out of it.
The V8 and 6 cylinder petrol models suck to fuel to much to make it of any use for a bug out. (In my opinion)

Here in Australia more Landcruisers are sold than in the US, so they suit our conditions. Have a look and see what sells where you are, and why they sell. Then look at what is the most reliable.
Then look at what suits you for your needs from the list.
I personally would be going for the Toyota over the Lexus.

Also you may find that one is better than the other, but the local backup is not as good. Pick the one with good backup.