I vote dump trailer. Assuming you're only going to use it a couple times a year, it will give you the best capacity without having a dedicated dump truck. Not just by volume, but by weight. That's the big one a lot of people will forget. Regardless the size of your pickup bed, or your rating (1/2, 3/4, 1ton), the actual weight capacity isn't much, and a dump insert is going to suck up a lot of it. A 1/2 ton pickup truck can only take about 1200-1500 pounds or so in the bed, but it can pull a 2,000 pound dump trailer with 3-4,000 pounds of stuff in it.