I won't say which is better, last thing I want is to get involved with someone attempting to debate the pros and cons.
I'll just suggest what I do on my computer. The decision is yours.
I use the external hard drive to store the System Image Backup.
In the search box next to Start, type file history > top left click File History > bottom left, click System Image Backup > Create a system image > plug in your ext hdd > follow the prompts.
I do that regularly, about once a month or after a bunch of updates have been installed etc.
Many times I had troubles I could not resolve. System Image Backup rescued me.
You can also create a System Repair disk, as well as a Recovery USB Drive if you want to cover all bases.