Mindfulness, Investigation of Mind Objects, Energy, Joy, Tranquility, Concentration and Equanimity. The Factors of Enlightenment are quite important to understand in the process of moment-to-moment meditation because sometimes there is a need for tranquility. If there's a lot of restlessness, you understand the tranquility factor of Enlightenment is needed. However when there is tranquility we understand tranquility alone doesn't get us enlightened, so we have to bring forth the investigation into mental objects so that we can understand the Truth. It is more of a balancing of the factors of meditation.
It is very difficult to say any one of these has more importance than another, because as far as the Noble Eightfold Path, the Seven Factors of Enlightenment are within the Noble Eightfold Path. They are within Right Mindfulness. So as far as what is the most important, I would probably have to say the Noble Eightfold Path is the most important, because it covers a lot of other things. For example Right Intention, the Ten Paramis could be raised to develop Right Intention. The Noble Eightfold Path is part of the Four Noble Truths, and it is the path leading out of suffering. When we understand the Noble Eightfold Path, we have a path leading out of Dukkha, and it includes all of the practice.