I don't think the Patriot would be as crammed as the others think unless its four pretty large adults. Mileage in the mountains won't be great, but its not great in any vehicle.
What it comes down to is this:
1. The new Grand Cherokees would be a better fit almost all around for you, but are far more expensive. Their base price is just shy of $30k when you get a 4x4 model. Add just a few options, and it starts to spiral up from there.
2. The base Patriot with the Freedom Drive II option is just a tad under $20k MSRP. Even if you load it up with every option available on a Limited trim, its still well under the Jeep Grand Cherokee's base price maxed out at about $28.5k.
3. The mileage will be about the same between the Patriot w/ FD II and the V6 Grand Cherokee. However, the Hemi Grand Cherokee would get even worse. Obviously power is no contest, but you can't get power and decent gas mileage.
What it boils down to is how much money you want to spend.
2012 Jeep Compass Sport 4x4
2.4L I4, CVT II, Freedom Drive I
2010 Dodge Dakota Quad Cab 4x4
4.7L V8, 545RFE, Big Horn Edition