If I were going to be traveling more, I would like the double axle trailer. I have a tr-20 with a single axle trailer, and I haven't had any problem with it, but I am only a 10 minute drive from the lake. I don't think the fuel economy would change much between the two, but I may be wrong. It seems like the double axle trailer would tow a little better, and the wear on the trailer, tires and axle would be more evenly distributed as opposed to the singe. The doubles definitely look cooler. For and 18 footer, I don't know if it would make a huge differnence, other than price, and maybe re-sale value.