For those who are not aware, these are two different types of backups that are available that are meant to be very useful for people who would need to hold quite a large amount of important data. Differential backup will make sure that it will back up the data that was saved since the last full backup. This is usually faster and easier because this does not need to backup all the data in full.
Incremental backup will back up the data since the data has been changed in the last backup. Incremental backups are known to be more reliable but they usually take longer as compared to differential backups. If you know that you need to store more data, differential backups are better.