Since the "broth" (or stock, soup base, bullion cubes/powder) will be the foundation flavor of your soup - it depends on your application, and the flavor you are trying to achieve. In addition to beef and chicken there are pork, lamb, fish/shellfish and vegetable stocks.
Give us an idea of what kind of soup you are trying to make and we can be more helpful in selecting the correct flavor base for your soup.
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain