The 3.7 V6 simply isn’t enough engine for such a large vehicle. I would not be surprised the V8 models actually get better real-world fuel mileage. If it were me, I would go with the Hemi. The EPA says that the V6 model gets 14 city and 19 highway. The 4.7L V8 is rated at 13 city and 18 highway. And the 5.7L Hemi V8 is rated at 13 city and 19 highway.
Doesn’t make much sense to go with the V6 IMHO.