Both apps can also perform designated tasks — for example, running shell scripts; ejecting the destination drive on completion; or instructing your Mac to sleep, shut down, or restart — before or after a cloning operation. (In Carbon Copy Cloner, such actions can be specified only for scheduled tasks.)
In my testing, both apps functioned impeccably, copying everything exactly as they claimed they would, including all the finicky OS X metadata, permissions, and links.
However, beyond the basics, the two apps diverge in interesting ways — each one offers useful tricks that the other does not.
SuperDuper's sandbox and special options
SuperDuper has two post-run options that Carbon Copy Cloner lacks: It can create a disk image of the destination volume (useful in an institutional setting where you may need to copy an image to multiple Macs), and it can install a package-based app on the destination.
In addition, SuperDuper has a feature called Sandbox, which requires some explaining but turns out to be very useful in certain situations. When you create a clone using the Sandbox option, the contents of the source volume's /Users folder (and, optionally, the non-Apple apps in the /Applications folder) aren't copied to the destination. Instead, SuperDuper creates symbolic links of those items from the source to the destination. Because so many files are merely being linked rather than copied, a Sandbox clone takes much less time to create than a regular clone, and it occupies less space on the destination drive. When you restart your Mac from the Sandbox volume (assuming, of course, that the source volume — typically your normal startup drive — is still connected), everything should behave almost exactly as if you copied all the files. But any changes to the contents of /Users (such as modifications to documents in your home folder) are made on the original drive, not the clone.
What's the point of all this? For starters, you can safely do anything you like while booted from the Sandbox clone — upgrade OS X, install new software, try out wacky system customizations, or whatever — and none of those changes will affect your original drive. However, you can also feel secure knowing that any changes you make to documents and settings while working from the clone will also show up when you switch back to the original drive. (Note that if you use the "Sandbox - shared users and applications" option, updates made to linked third-party apps while running from the clone will affect the original drive.) This makes a SuperDuper Sandbox a great way to test, say, a beta version of OS X. SuperDuper's documentation cautions that you should not treat a Sandbox clone as a replacement for a regular clone, but as a supplement for testing purposes. The developer also recommends against restoring a Sandbox clone to the original drive.
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