Monica, I have to agree with Cruise Fanatic. For your first cruise, I would rely on a cruise professional that can match your expectations with the appropriate cruise line and specific ship. Even within cruise lines, there are different types of ships, each with their own personality and fit within the marketplace.
The differences in opinions regarding ships stems from the fact that one reviewer may have been perfectly matched to their ship, while the next one (on the same sailing even) may have been a perfect mis-match.
The passenger loads between Holland America and NCL are like night and day. It all depends on you and your expectations and a cruise professional will make sure you are properly placed.