I have 80,000 miles on my 2012 VW Touareg 3.0. It won't pull a 5th wheel, but it does have the dreaded Bosch 4.2 HPFP. There was one temporary electrical problem with that vehicle early on, but absolutely nothing else since. The only extra maintenance with the diesel on that model is the fuel filter every 40K, which runs about $100. This is a daily driver and also gets driven on some very long road trips. We got the diesel for its towing ability.
My 2012 F350 is a 6.2 gasser with a 5,000 lb TC on it. The truck sits in outdoor storage for as long as 2-months at a time without being used. 60,000 miles and no problems. We got the gasser because we knew it would sit for long periods of time and wanted the lighter overall weight. This is a notoriously reliable engine requiring little maintenance. I wouldn't want to pull a large 5th wheel with it, but opinions vary on that one.
Each choice was based on intended use. If you want/need the torque of a diesel you are going to pay the price of higher fuel prices (usually), slightly higher maintenance costs, higher upfront costs, and need for DEF, but I don't think reliability is a valid concern with any truck after about 2011.