What's the difference?
Both require a full backup of the data set to be performed first. Once that is done, both require only files that have been changed to be backed up. However, it is after this initial backup that these strategies are vastly different.

With incremental backups, if you change even one letter in a 32KB word processing document, the entire file, all 32KB, gets backed up. With Delta technology, only the piece of the file that was changed gets backed up again.

As an example, let's say you subscribe to a service that uses incremental backups, Low Prices Inc, and you are backing up 1 Word Processing document of 32KB (about 2 pages). You change one 256 character paragraph every day for seven days. The amount of data being sent to and stored with this backup provider (using incremental backups) just shot up to 2 Megabytes of data; in one week! The red bars above represent the incremental backup storage amount.

Using the same scenario with a backup service provider using Delta Technology, such as SDS, the data storage increases from an initial 32KB to only 33.5 Kilobytes (green bars).

Then there's bandwidth to consider. Using an incremental backup, a 100MB data backup over a dial-up modem will always take about 7.1 hours. With a Delta backup, that same backup could take only a couple of minutes.

Even though the initial prices may seem much lower, clearly there is a large financial penalty for using a backup service provider that uses incremental backups as opposed to one using Delta technology. That's why backup service providers using incremental backups often have much, much lower prices than those using Delta Technology. We use Delta Technology!