2001 Jeep Cherokee

Both sound really nice. However, I have to be honest, the only thing I can tell you is how long the vehicle will last is based on how well it has been taken care of over the years. The extra miles on the one may not hurt a thing if it has been properly maintained. That is something you and I have no information on.

If it was me, I think I would go with the one with the nicer equipment. The mileage, as mentioned, isn't that much higher, but again prior use determines how long it will last. Will they drop the price since the mileage is so high?

Without being able to see the vehicles for inspection, it's hard to say which is a better buy.
I can tell you the Grand Cherokee is a more plush model with a better resale value. You will also normally have more engine options with the Grand Cherokee.
I would recommend driving them both to see if you notice any unusual vibrations or noises. Also, allow it to idle for a little while to see if any abnormal idle shows up.
Check all of the fluids(oil,transmission fluid,coolant, etc..)to see if they are low or in poor condition. Check out any maintenance records to see if it was serviced on a regular basis. Carfax is also helpful.
Most important, take it to a reputable mechanic for an inspection.It's going to cost a little for the inspection, but it could save you from a $4200.00 mistake.

As for the engine reliability, in line 6 cylinders are known for broken exhaust manifolds. The V-8 model is known for bearing failures if the oil has not been changed on a regular basis.(look for loss of oil pressure under hard acceleration)