Till where mechanical parts are concerned, available for both and in excess. As for body and interior parts, land cruiser takes the lead.
As for mileage of a Nissan patrol, if it's a non turbo manual vehicle, does 7 local, 10 long. If turbo, 5 local 8 long. But if you know how to attain economy, the turbo can give better figures as well.
As for ruggedness and maintenance, both are sort of the same, the major difference is that a grown person cannot sit in the second compartment of the Nissan.
All that said and done, I owned a Nissan Patrol for about an year and loved every second of it. A good 93 cruiser is hard to find, the ones that are there are insanely priced.