On my last trip to the world I tried both the evening and morning Extra Magic Hours. There is a huge difference between the two and I am not talking about time.
If you take advantage of the morning hours you will be in a ghost town. I took a picture of the castle with almost no one in front of it and this was just before the park opened to everyone. By taking advantage of the morning hours you’ll be able to do a number of rides with little or no wait.
Evening Hours are a totally different animal. Most people will tough it out and do the evening hours. The parks are not only packed during those hours but packed all day long because they draw more people to that park. The only benefit you will get is if you stick it out until the last hour because people start to leave the parks then.
Overall people don’t want to get up early but they are willing to stay out late. Keep that in mind when deciding if you are going to take advantage of the extra magic hours.