Which one is better mercury mountaineer 2002 or ford expedition 2001-2002 ?

Mountaineer is the same as Explorer, expedition is better

There was a major change in the rear suspension on the '02 models ( pretty sure it was '02 ) with the addition of the rear independent suspension. They ride better, corner better, and sit a bit lower. But, if you want to pull something big/heavy, and maybe lift the truck a bit, or add heavier rear springs or shocks, you don't want the independent suspension, it will only complicate those modifications. So, that's the question to you, which do you want ?? Then look for the Ford or Mercury that fits.

Basically, it's the same vehicle. The Merc will have more options and amenities. I'd choose whichever one had the V8 engine......