Most of these class C motorhomes are on E450 chassis which has as much (or more) payload margin than typical pickups pulling a trailer. I don't anticipate undue mechanical issues on my Ford cutaway. The hand built "coach" tends to be the most problematic-and that exists whether in a trailer or a motorhome. Additionally some RV coach products such as air conditioners, skylights, toilets, refrigerators, etc. seem to rank lower on the reliability scale than many consumer products. Again, though same stuff on a motorhome vs. trailer.
I'm happy I made transition to class C from a trailer. It certainly has not been more upkeep when taking tow vehicle into consideration.