There seems to be a debate in the shooting community as to which type of load is better for home defense, buckshot or birdshot. This debate may never truly be settled because it comes down to your particular situation and preference.
The biggest difference is penetration and range. For most home defense situations range is not a huge factor. Most encounters will take place within 10 yards and that range both do a ton of damage and will easily neutralize a threat.
The thing you have to worry about is penetration. If you are living in a confined space with neighbors or possible kids in the next room you might not want to use buckshot because it is going to penetrate further and you run the risk of a pass-through hitting an innocent person. However, if you live in the wide-open country a little extra penetration and range might be better for you.
It is a decision you will have to make based on your circumstances. Check out this video from FMG Productions as they shoot both rounds and give the pros and cons of each.