Ok, I have a Dodge 1500 Quad cab with the 5.7 hemi.
I also have a Dodge D350 (3500 series) with the 5.9 Turbo diesel,
The hemi has 345 horsepower with 375 lbs of torque,
The diesel has 160 horsepower with 400 lbs of torque.
Both are pretty close to evenly matched. Of course Torque is the factor.
Both trucks pull 8,000 lbs pretty much the same, The hemi getting around 14 mpg loaded, the diesel around 17 mpg. Empty the hemi gets 22 to 27 mpg and the diesel gets around 22 to 27. (almost perfect conditions mind you,)
As far as maintenance, The hemi requires the spark plugs to be replaced every 40,000 miles, (no cap,rotor etc,) Ignition wires around 75,000 miles, Oil changes every 7500 miles along with fuel filter change every 10,000 miles.
Oil capacity is 8 quarts, incl. filter
The diesel needs oil changed every 5,000 miles, along with dual fuel filter and water seperator. Oil capacity is 16 quarts incl. filter. An injector failure on a hemi is $116. ea. On the diesel and injector is around $400. A fuel pump on a hemi is $134. and a fuel pump on a diesel is around $419. (turbo's on a diesel can run from $800 to $2200).
Depending on your financial arrangement, Diesels are nice, BUT, are a bit more expensive as far as maintenance and repairs, The diesel is made to pull heavy compared to a gasser.
Im NOT endorsing Dodge, but I have run Fords and Chevy's,, Ford makes an almost bulletproof 7.3 diesel compared to Dodges 5.9 Cummings workhorse.
Chevy diesels are somewhat OK, But still have a few bugs to work out as far as injector and engine heads getting overheated. A good rule of thumb is its better to have a little more power then you need , then to be underpowered when needed most. F.Y.I. A ford powerstroke 7.3 is expected to have injectors replaced at 100K,, so if your planning on buying a used diesel, ask if the injectors have recently been replaced and if not, expect a chunk of change to have them replaced. Hope this helps a little bit when deciding a gasser verse diesel.