Depends on your needs. Honestly, you can possibly beat (or at least equal) this level of privacy by using Firefox with the Arkenfox user.js and a couple add-ons (uBlock Origin, for one). This is what I do.
Out of the box, though, Mullvad Browser is going to be more private and more hardened than plain, untouched Firefox. This means users can achieve much better privacy with no more effort than downloading the browser. For someone who doesn't want to do any tinkering, this is a great option. Mullvad Browser also has a portable version, which is cool.
The advantages of Firefox + Arkenfox over this are more customizability and faster updates (meaning you get security patches sooner).