AAaaaaand how they differ from Alpacas!!
The final difference I will mention is the use of llamas for guard use. Oh yes, llamas are regularly used to guard other pack animals, such as the alpacas above, but they are also used with sheep. The llama is great for this work because it will literally stomp on the attacking animal in order to protect it's herd.
All in all, both animals are super awesome. And, through personal experience, they are also very nice animals. Granted, there are always a few bad apples (spitting, anyone?), but they usually only do it as a show of dominance, so don't sorry about it too much. Just don't get up in their faces, and you should be fine.