The diesels are more expensive to buy and maintain, but last longer. When we went to Windrock last April we had 4 big utility 4x4 quads with all out gear in a 28' enclosed trailer. We pulled it with my father in-laws new one ton dually 4x4 crew cab chevy it has the Duramax diesel and Allison transmision. We figured the trailer weighed 9000 lbs which was not a load for this truck. We got 18 mpg towing down there, around town to the hotel and trail head and back. That is pretty good I thought, considering the mountains we had to tow through. But an oil change for that truck is over $30 and other parts are higher as well. If you towed a lot of heavy stuff this would be the way to go. But in the long run just using it for transportation it would be more cost effective to have a gas motor. But I like the diesels as well, and will have one some day.
About the Toyotas, I have a 98 Tacoma 4x4 with the 4banger and 5 speed on 31" BFG MTs. I drive 34 miles a day one way to work and I get 24 mpg. I can pull two quads on a trailer up the hills we have around here which aren't that much, at the speed limit. It has plenty of power and the quality is much better than anything I have ever had before. I have 78,000 miles on it and have done nothing but gas, oil and filter changes and clean the K&N. That is why my wife now drives a Tundra. The Tundra is made right down the road from my house I have several friends that work there. I work construction and worked on the plant for over 18 months. I believe the quality of the Toyota trucks is much better than the big three. Just my opinion.