While some cruise ratings give you only a general score for the ship, others break down the experiences into specific categories. Some examples of categories include dining, entertainment, cleanliness, service, value, and stateroom quality.
The rating categories can be helpful if there are some areas that are particularly important to you. Perhaps you are willing to accept low-level entertainment if the value is right. Or maybe on-board activities are something that really interest you, and you are not willing to settle on that point. Think about what you want, see what your options are and then check the ratings.