Search the forum, and go to the other ram forums about the diesel, just make sure you are reading about the new 3.0 version. A lot of complaints about the older version that came out in 14’. As far as towing with the hemi, it will do what you want easily, just gets 8-10 doing it.
Non-towing highway mileage will depend on gearing and speed, the best I’ve seen regularly reported is 21-22 at maybe 70mph on flatter terrain with 3.21’s, no lift and no aggressive tires. 3.92’s seem to average 17-18 highway, give or take again without lifts or changes in tires.
Lots of mpg threads with some real unhappy owners and some claiming near Prius mileage, lol. Here’s my average highway mpg bone stock (see image).
In short, you’ll want to compare expected maintenance costs (more expensive oil changes and fuel filters) and more expensive fuel (some parts of the country are .70-1.00 more per gallon) against the return when you sell (a plus for diesel) and better highway and towing mileage.
If you like performance then you might be disappointed with the diesel. If you want mpg’s then diesel is better. You don’t tow heavy enough to strain a hemi.
That’s a tough call.