Perhaps the main difference is that the one (the "haba") originated in North Africa and the other (the— the one English speakers call a lima bean (or a butter bean) and that Spanish speakers might refer to as a "pallar," a "guaracaro" in Venezuela, a "garrofón" in Spain, or simply "frijol" or "haba" de lima elsewhere(de lima) elsewhere — originated in South America. They look very similar, so it is not surprising that they are mistaken for one another, but they differ somewhat in appearance, taste, and composition. From personal observation, I notice that the lima bean tends to have a grainier appearance than the fava (or broad bean). Below is a side-by-side chart of the lima bean and fava bean so that you can see how similar they look:
In the rest of the Spanish-speaking world the "haba" is usually just a common dry bean and though you might not see it paired with "blanca," it is paired with "negra" (for "black bean") or "roja" (for "red bean"). Keep in mind that the other names for bean listed previously are far more commonly used and paired with descriptions of color to differentiate specific types of a dry bean. The word "haba" is also known by many as the word to use for "coffee bean," but there are others. More on that later at the end of this answer.