For 2012 models of both vehicles, I'd say both Pajero Mini and Jimny are same. Both are imported ones, so quality of build is great and long lasting. With turbo are good with needed power when needed.
Parts availability is also not an issue for both. Every big city have common consumable parts and if there's need for mechanic, no shortage as well.
Fuel average is almost same if both models have same capacity engine with turbo.
Your choice should depend on your budget, then condition of the vehicle. If your budget allows, go for one which is not used much locally.
Make sure no local mechanics did any major work on engine, gearbox or electronics.
Best wishes for you to find a good one.