If you are buying a truck to specifically tow cross country pulling a family size RV trailer get the diesel. gasser is fine if you are a weekend warrior but if you are crosscountry towing you will want the power, fuel range and fueling cnvenience of a diesel.
A lower priced truck is no bargain if it is the wrong truck.
Keep in mind most any diesel will do what you want,however you will need to be selective and choose the correct/right truck if you go gas.
Even then the gasser will not equate to a diesel.
The diesel difference is for real when it come to cross country RV towing.
19'Duramax w/hips, 2022 Alliance Paradigm 390MP >BD3,r,22" Blackstone
r,RV760 w/BC20,Glow Steps, Enduraplas25,Pedego
BakFlip,RVLock,Prog.50A surge ,Hughes autoformer
Porta Bote 8.0 Nissan, Sailun S637