Manually backing up or have it set to automatically backup?
Automatic (scheduled) backup is not exactly continuous backup. You can get truly continuous backup with the proper RAID array, and if you can afford enough drives and the raid controller to do it, you will not even suffer a performance cost. If you are running a mission critical service, that might be worth the cost. But for most of us the purpose of a backup is to avoid losing more than the current work session if your drive fails.
Problems with scheduled backups are that they may start to run when you want the machine to be doing something else, or that the machine may not be running when you have scheduled the backup, or that the failure will occur before the backup is scheuled to run. Those problems are avoided by doing a manual backup when you are ready to save something important. The problem with manual backup is that you may forget or otherwise avoid doing it often enough to save what you want to save. I personally find it easier to backup manually, than to come up with a scheduled system that will work. But my machine is pretty much under my control, not running programs while I sleep etc.