I don't know why people on this forum go around saying that you can't boot from a Time Machine backup. As of OS X 10.7.2, Time Machine backups are bootable. They won't boot into the version of the OS that you were running, and you can't log in to your account, but they will boot into the equivalent of your Recovery Partition. From there, you can reformat disks and do a full restore.
If your Time Machine backup is slow, or if you want to be able to restore things more easily, check out:
BackupLoupe ($10)
BackupLoupe: One Stop Shop for Time Machine
There are good reasons to have a clone backup (e.g. SuperDuper or CCC) and there are good reasons to have a versioned backup (e.g. Time Machine.) Ideally, you'd have both. But if you already have a Time Capsule, and you only intend to do one sort of backup, there is no reason not to go with that, especially if you use a third party utility to make it more useful, such as:
Back-In-Time ($30)
http://www.tri-edre.com/english/backintime.html
There are two basic kinds of backups that you can do of all of your data: a "clone" and a "versioned backup."
A "clone" backup basically creates an exact duplicate of your main hard drive *as of the time of your last backup*. The clone will usually be bootable (that is, you can startup from it), just like the original drive. This type of backup is wonderful to have if you have a catastrophic main hard drive failure, or even if your entire computer is stolen or destroyed. If you have a clone backup all you have to do is designate the hard drive with the clone backup on it as the startup disk in your System Preferences (on any Macintosh computer), and you can go on with your work/life as if nothing happened. (At least as of the date of your last backup. That's why it is important to schedule frequent incremental backups.)
I recommend SuperDuper to make a clone backup:
SuperDuper!
but some users prefer the very similar program Carbon Copy Cloner:
http://www.bombich.com/index.html
Time Machine
macOS Sonoma
does what is known as a "versioned" backup. Instead of creating an exact duplicate of your hard drive, an archive of everything that is now, or *ever has been* on your drive is created, *as of the time of every single past backup*. This type of backup is very valuable if you accidentally trash something that you find that you now need, or if you find that you need a previous version of a document that has since been changed. If your main drive fails, you can still restore it from a versioned backup, but there will be quite a bit more time and work involved than with a clone backup to get things approximately to where they were before your main drive failed, and to create a drive that you can boot from. You will also need to purchase another known good hard drive to create the restored bootable drive on.
In my mind, a clone backup is essential. There are ways to get some of the advantages of having a versioned backup without actually having one. One way to prevent trashing stuff and regretting it later (thus obviating much of the need for TM) is to create a new folder on your desktop and call it something like "Pre-Trash." Don't put stuff you want to get rid of in your Trash. Put it in Pre-Trash instead. Inside of the Pre-Trash folder, set the View to By Column and click on the Date Modified header and click on the Date Modified triangle to have the column show the oldest files first. Every now and then you can go into this folder and manually delete files over a certain age. For example, you can delete files that are over three months old...once you are sure that you will absolutely never need them again.
Is there a valuable reason to have a versioned backup in addition to a clone backup? Yes, a really good one. If the data on your Mac's hard drive becomes corrupted, or hopelessly infected with malware (of a type that does not yet exist), and your clone backup software runs before you detect the problem...all of your data, both on the source and the backup, will probably be destroyed or ruined. However, if you have a versioned backup, even if it has run subsequent to your data being compromised, you can still completely recover your data using the versioned backup.
Much more information about backing up:
Backing Up Your Mac
$15 (currently on sale for $11.25)
210 page ebook in PDF format.
3.1 MB download
Take Control of Backing Up Your Mac – Take Control Books