I plant 16ft of pole beans on 7ft tall hog panels every year, and I like a variety, both for flavor, texture, and to cover bases for seasonal growing variances. After trying many varieties, the ones that I go back to every year are: Rattlesnake, Fortex, Carminat, Red Noodle, Yard Long, and Goldmarie. If I had to limit myself to one, I would pick the Rattlesnake, at least for our Sacramento climate. It's always the first and last to harvest, heavy crops, tastes great, is more forgiving in picking size, and easier to pick due to the purple mottled color, which stands out better among the leaves.
Yard Long beans are fun, and you can use them as a base for a meal, instead of pasta. They add a nice texture variety. Also great for stir fry, since they are skinny. These purple ones add even more variety, and are easy to pick because of the color.