SparkyLinux vs MX Linux

You have access to a large user repository, Ubuntu guides can mostly be applied since both are based on Debian.

You have the option for Sparky to be based on Stable or Non-Stable, bringing greater flexibility to user priorities.

Sparky is designed to be lightweight in it's core. It is based on Debian but optimised for old hardware, meaning you can run a full heavy desktop environment on a lightweight foundation, bringing greater performance compared to similar Debian or Ubuntu-based distros.

Any Linux desktop in it's vanilla form can be installed on top of Sparky, whether that be alongside a pre-existing environment, or on top of a basic command line system. Furthermore, the command line system is easy to operate due to Sparky's advanced installer utility, from which you can choose whichever desktop environment you desire, straight from the Debian repositories. Guidance is on their website.

Can create your own ISO (snapshot) and use it either as live-session and install back when needed.

With the (pre-installed) Snapshot tool you can easily create an ISO of your running system and then save it to a USB (or other media) and use "your own" distro as a live session or install back whenever you like (even on a different PC with different specs with no issues). You can even give that customized ISO to friends (selecting "non-personal" ISO when creating the snapshot; thus resetting the accounts & passwords and Home folder etc.).

Also you can save that ISO directly encrypted via MX Live USB Maker tool. Again, you can install MX encrypted during installation with just ticking a box, no matter if it's the official ISO or your snapshot.

MX Linux comes with its own set of tools called MX Tools, designed to make life easier for users.

It is based on Debian and not based on Ubuntu.

It has almost all tools to repair non booting systems or recover files & folders and save them on a safe place. And when thought together with it starts quick on live-session. In addition, you can do these with "your own", customized distro (snapshot).

After Puppy Linux (which's aimed to run from RAM and which is smaller in size) the second fastest (head & shoulders) booting one (together with the sister project antiX) and also has the option "toram" to run from RAM. Yes, not only when compared to full distros, even far faster than small sized or tiny distros, especially when booted to "live-session", about 2 - 2.5 times faster on an old single core laptop.