There are various differences between Differential and Incremental backups. The major difference is that the Differential backup will contain all changes since the Full was last taken. The Differentials grow larger over time until a new Full is performed. The advantage is that you never have more than two points in time to pull a restore from. This could be bad for storage unless deduplication is possible at the block level. If the blocks are two unique, then the amount of storage used can be extensive.
VMware's Change Block Tracking technology feature allows Unitrends to perform incremental backups. When used with our Incremental Forever strategy, Unitrends only needs to perform a 1-Time Full on the VM to collect all blocks, then works with VMware's CBT to collect the changes. Unitrends will then create a Synthetic Virtual Full backup by reading the full backup and the incremental backups to create a new Synthetic Full backup file with all the contents of the previous backup chain set. The new Incrementals will reference the new Synthetic Full, and continue from there. This is a great way to reduce the stress on primary storage and on the Hosts and Guest VMs while still having a complete restore point, that restores faster. You must ensure that CBT is Enabled to utilize this Unitrends functionality.
To get a better understanding of our backup process and the benefits off the Incremental Forever strategy, please read KB 3560: When are synthetic backups created?