Do you plan on doing any towing?
Are you actually going to have a need for the truck bed?
Both vehicles have the sames trans (4.7L and 3.7L), and it's a relatively solid transmission. You'll see close to the same gas mileage with both vehicles, probably slightly better with the Liberty.
I owned an '02 Liberty Renegade and the only issues not caused by me lifting it and beating the piss out of it was a TPS sensor and small EVAP leak which were both covered under warranty. I took it up to roughly 75,000 miles.