Help choosing a dog!?

I have two dogs right now. I need to choose one to keep. The beagle mix dog is very scared when visitors come, and runs away. But when we are on a walk, she starts to bark like crazy at the people. Also during the night she always barks. She has a lot of energy, buy she is very sweet and always wags her tail at me. But she does sometimes play bite you when you pet her. The other dog, German shepherd mix, is really calm, and she almost never barks at the people when we walk. She is really quiet, but really sweet. She is the perfect dog, but only when people approach he wrong (lean forward and pet her head) she (actually) bites them. On the other hand when the dog gets time to sniff the person (outside the gate) she is very friendly. I am scared that if we choose her (German shepherd) she might snap at one point, and bite somebody really hard, and then we would have to have her put down. Please help me.