It depends on the shape of your face. If you have a long face, then a medium or long beard will suit you. If you have a round face, then a short or medium beard is best for you. It also depends on your personal taste. You can try different beard styles. The type of hair also matters a lot. If your beard's hairs are straight, then you can keep it long. But if your beard's hairs are curly, then keep it short.