Bush beans are the way to go for a container garden, while pole beans take up less garden real estate because they grow up instead of out.
Before you pick up a seed packet for green beans, note whether it's for bush beans or pole beans. The difference (as you can probably guess) is that bush beans grow compactly, closer to the ground, while pole beans grow vertically and need some kind of structure (like a trellis or fence) to climb up. Bush beans are the way to go for a container garden, while pole beans take up less garden real estate because they grow up instead of out.