Men pushing barrows and carts moved the stuff that built civilization, and aside from the addition of a little power and rubber tires, not much has changed. From trash to topsoil to building materials, everything travels more quickly when you stick a wheel underneath it.
Carts and wheelbarrows help you move heavy loads by distributing the weight over the wheels. A wheelbarrow has a sloped tray and one or two wheels in the front. You have to push it, but it maneuvers easily and can go anywhere (provided you don't jam it into a hole). A cart, on the other hand, has straight sides and two or more large wheels. It works best when pulled—ideally over a smooth surface, though its big wheels can bridge holes. Carts are also more stable and carry more volume than wheelbarrows.
When choosing either, follow the recommendation of This Old House landscape contractor Roger Cook to look for foam-filled or solid tires, because pneumatic tires can go flat. And when it's lunchtime, do what Roger does: Throw a piece of plywood on top and set out your picnic spread.
Shown: A powered cart, like this electric model, can make moving heavy objects up and down a hill a real breeze.