Having bootable backups was the only reason I ever moved to a Mac.
This means, a backup of my computer created using something like Carbon Copy Cloner, or SuperDuper backup when plugged into any other Mac, and it would boot as my computer. Also known as Target Disk Mode booting off this backup.
Indispensible when or if my laptop was in for repair with Apple.
TimeMachine is a pretty good second option. It's not bootable itself, but the recovery console on any mac can ingest a time machine backup and get you back up and running quite quickly. The benefit here is that it's free, trivial to setup, and very easy to keep running; Given an empty disk, plug it in, click one button, done.
Time Machine is OK as secondary, never primary, or the sole option.
Having Target Disc Mode and Target Display Mode on a Mac are two of probably the 4 reasons I switched to a Mac from Windows. Skitch was the other, and CC/SuperDuper was the 4th. I had tolerated my last windows laptop dying :)
Multiple copies of multiple types of backups is the only way.
I have always maintained a CarbonCopy/SuperDuper at all times, plus a Time Machine that I cared far less about. Time Machine is my desperate fall back.
Time Machine backups haven't always been super reliable, nor is the recovery time to restore acceptable. I'm sure it's gotten better, but enough for me to forget what it hasn't done in the past? Doubt it.
Time Machine is kind OK for set it and forget it backup to a NAS or something. I didn't find as much value in Time Machine to a dedicated external drive since it had the risk of being the only backup, and it's not a backup if there's only one copy. Time machine's limited utility of use when there is an emergency on an external drive, compared to SuperDuper/Carbon Copy Cloner which is you are up in minutes not hours or days while you figure out what is going..
Having a Carbon Copy/Super Duper external drive sitting at one of your desks that's regularly plugged in gives you a live replica should anything happen.
Having bootable backups was the only reason I ever moved to a Mac.
This means, a backup of my computer created using something like Carbon Copy Cloner, or SuperDuper backup when plugged into any other Mac, and it would boot as my computer. Also known as Target Disk Mode booting off this backup.
Indispensible when or if my laptop was in for repair with Apple.