Figure out the amount of weight you will be hauling and size the trailer capacity appropriately. An overrated trailer will beat the snot out of your cargo. An undersized trailer will break down at the worst time and place possible.
Tandem axles are smoother riding and more stable, but you have twice as many tires to replace and twice as many bearings to maintain. A flat is less serious, but more likely to happen. They are also much harder to push around by hand if you need to re-position slightly.
Jerry
