Both Monteros and XJ's are now going to be either a beater (around town, not traveling) or a novelty (you treat garage time as recreation of its own sort, clean and fix stuff the same way other people might work in a garden...) - I would not consider either one of those vehicles for travel if I wasn't also planning to put a ton of work and money into their long term repair and maintenance. Entropy makes no exceptions here.
So:
- If you want the classic car experience with Saturdays in the garage performing recreational maintenance, and a great travel vehicle once you have committed the work (but keep that AAA membership up, too...) - a Montero is perfect.
- If you want an all purpose, all weather travel vehicle then you're going to want something less than 10-12 years old and which sold a lot of units so there's a lot of repair aftermarket (not to be confused with modification aftermarket) - that means grand cherokees, trailblazer/envoy/ascenders, durangos, libertys, 4runners, hummer H3's, tahoes, honda pilots (yes really).. and then you'll probably not want to change a lot about it.
Based on our experience I think you're being more negative than warranted. Our Montero has required zero work in 5-1/2 years - we follow the maintenance schedule rigorously, and have had to do nothing other than this. We did unintentionally adjust the exhaust downpipe once (hit a rock which we thought was a clump of grass - adjusted the gasket with a bit of "gun gum" and it's been fine ever since). Recreational maintenance - zero.
This has included a lot of travel on unsurfaced tracks, river crossings, mud, rocky surfaces, and sand.
We tried an XJ when we bought the Montero and although it would be a lot more capable in "rock crawling" mode it was not big enough inside, nor comfortable enough in terms of ride to be a viable option for overlanding (which opinion was confirmed on a subsequent trip in one in Canada.
re the other vehicles mentioned:
- grand cherokees - we've used one in Canada - good vehicle, but I wouldn't take one overlanding,
- trailblazer/envoy/ascenders, durangos, libertys, tahoes, honda pilots - ditto and most of these will present problems in maintenance and spares in much of the world,
- 4runners - had one in Congo and it was OK but the suspension was far too solid to be comfortable on the "roads" there.
- hummer H3's - I have difficulty imagining a less comfortable and practical vehicle for overlanding (having said which, I've never driven one, so am ignorant and so should have no opinion, other than based on the fact that I have only ever seen one in private hands outside a city - and that was in Switzerland on the motorway).