Pros and cons to every vehicle, personally not a huge fan of mitsubishis build quality in general but that said ive seen some pajeros get through tricky spots too.
A well maintained diesel will cost you less in fuel, diesel patrol, prado, hilux or pajero are good options.
Fuel economy is better than their petrol counterparts, but the trade off is service.
Letting a diesel goo too long without proper servicing is harder on engine componants than a petrol motor which can in turn cost you more in repairs.
Also as has been mentioned its worth thinking of the worst terrain you expect to travel through, this will affect the kind of suspension you will need.
Older 4x4s genrally have 2 solid axles which allow for more flex in the suspension and durability of the driveline when tackling obstacles like deep ruts and rock steps. However it makes for a more jostling ride as the suspension and driveline twist and sway in order to keep the most traction possible.
Newer vehicles early 00s onward tend toward a solid rear axle and independant front suspension which uses cv shaft to connect with the front diff.
During travel over rough terrain the front suspension has to work harder to keep grip and extreme angles will see it struggle to grip on one side. This in turn causes more wear on driveline cvs and diff internals.
Having this type of suspension makes for an easier ride though and allows a large 4x4 to handle like a large sedan on road.
Its also worth paying attention to the chassis as bogger mentioned. It varies depending on make and model but most medium to large 4x4s and some small ones have a separate body bolted onto a chassis frame to which the motor, driveline and suspension are attached.
This means that tortion of the chassis during rough offroading or pulling a vehicle free wont twist or stretch the bodywork above.
Its easy to see the difference, when you look under a 2 piece body and chassis you can clearly see the large rectangular tube frame and the rubber mounts that join it to the body above. As opposed to a 1 piece or monocoque chassis where the body is moulded directly to the chassis and all other components are bolted onto the one piece.
https://www.prospectingaustralia.com/forum/img/member-images/784/1474722575_images.jpg
Example of a Solid Front Axle.
https://www.prospectingaustralia.com/forum/img/member-images/784/1474722733_images.jpg
Example of Independent Front Axle.
https://www.prospectingaustralia.co..._land-rover-discovery-chassis-replacement.jpg
Example of 2 Piece Chassis.
https://www.prospectingaustralia.com/forum/img/member-images/784/1474723296_images.jpg
Example of a monocoque chassis.