MX Linux is Debian-based.
Manjaro has Pacman for its package manager (the thing which allows you to download software), which is command line interface. I can't abide that.
MX Linux has Synaptic Package Manager and MX Package Installer by default, which aren't the most intuitive but are still far better than any CLI-based package manager.
Honestly I'm surprised any distro can be called "user-friendly" (how Manjaro is referred to on its website) these days if its package manager is CLI. I know another package manager can be added, but still, come on. Anyone who's old enough (me included) and used "regular PCs" will remember leaving behind command line stuff as of Windows 95 (with the odd exception). I barely remember any DOS commands. As for new users, they're not going to appreciate CLI stuff either since most computers these days are as GUI-oriented as possible. Realistically speaking, most users won't find some very important aspects of an Arch-based distro such as Manjaro "user friendly". If they mean "programmers, and hardcore Linux nerds will consider Manjaro to be user friendly", fair enough.
Also it seemed there was a wider variety of software repositories for Debian (MX Linux). That is unless you count the AUR with Manjaro (and they warn about possible issues when doing that).
There were a few other things I noticed about MX Linux that seemed more friendly, including the ability to make a custom ISO (for doing backup/restore).
Anyway in a video I'd seen about MX Linux versus Manjaro, someone commented this:
So consider what sort of user you are, and what you need in terms of "user friendliness".
I'm sure I could "deal with" Manjaro as well, but I don't want to bother with the extra work.