Those little wrapped cubes of bouillon are loaded with flavor, but granules are essentially the same thing in a different package. Both dissolve in liquid and both can be used alone mixed in water as a thin soup, or added to other ingredients for a heartier dish. Choose the one that best suits your own cooking style and read the ingredient list, since many are loaded with salt.
Bouillon granules and cubes contain essentially the same ingredients and many companies make both. Bouillon cubes and granules are essentially concentrated chicken stock that has been dried. Granules have been ground, while cubes are pressed and formed into squares.
Whether you choose bouillon cubes or granules is mostly a matter of personal preference and convenience. Bouillon cubes are pre-measured, so you know exactly how much bouillon you're using -- typically 1 teaspoon. Granules, on the other hand, must be measured out, but you can add exactly the amount you want, whether that's 1/4 teaspoon or 1 tablespoon. Granules are easier to control than bouillon. If a dish needs just a tiny bit more flavoring, you can easily measure out a small amount.
One advantage of granules over bouillon cubes is that they dissolve almost instantly in water, whereas bouillon cubes takes several minutes to break down. If you're seasoning a dish, you must wait for the bouillon cube to completely dissolve before assessing the flavor. If the bouillon cube hasn't dissolved completely and you add more cubes or seasonings, you might add too much. Granules, on the other hand, sometimes cake together during storage, which is never a problem with bouillon cubes because they're wrapped. If this happens, use a spoon or knife to stir the granules and break them apart.
Both granules and bouillon make quick work of seasoning soups, stews and casseroles. More important than the form of bouillon you use, though, is the quality of the product. Some bouillon cubes and granules contain little more than salt, monosodium glutamate and sugar. These products have a strong chemical taste and aren't particularly healthy. Instead, look for high-quality products that contain real chicken, chicken fat or chicken stock, along with vegetables and spices, such as onions, celery, carrots and parsley.