Between the two trucks you list, if it were me, I would buy the new Ram. Just seems like a much better value for only $5K more.
However, if it were me, I would keep shopping and find a 3/4 ton within my budget. Even though you aren't towing very heavy, 3/4 ton is always a better and safer towing experience. Plus that gives you "insurance" against having to upgrade tow vehicles if you ever move to a larger and heavier RV (which most of us have done). And all other things being equal, resale should be a little bit better for the 3/4 vs 1/2 ton.