There would be advantages of moving to a Debian base.
Debian now uses calamares as the default system installer. It is actively being developed and new features etc being added on a regular basis. It is not harder to use than Ubuntu's ubiquity installer if configured properly. Ubuntu has plans on moving away from the Ubiquity installer.
Snaps are becoming more and more of an issue. They may make sense on IoT and maybe in the server realm. Canonicals main source of income is from the server market and that will always take priority over the desktop. My opinion, and my opinion only, is that flatpaks will become the dominant universal package format.
Debian moves slowly and takes their time to implement changes. Canonical / Ubuntu has a much less predictable path.
Ubuntu is not based off of the Debian stable branch. LTS releases are generally a snapshot of Debian Testing and non LTS are a snapshot of Debian Unstable .
There are disadvantages of moving away from a Ubuntu base.
The work required by the Zorin brothers would increase with a Debian base.
Basing off LTS releases allows for fairly recent kernels etc through the HWE stack.
Each branch of Debian requires careful consideration.
Debian stable in order to stay current eventually requires the use of backports or the Zorin devs having to build their own packages. As debian stable ages it becomes necessary to use more and more hacks to get around dependencies etc.
Debian testing. Mint learnt their lesson with what happens when Testing gets frozen before a new stable release. It can be used but requires a lot of work.
Debian sid. Definitely not what I would recommend for a new user.
Most of the MX Linux devs are from the Mepis days. They have 15 + years of working with Debian stable and know workarounds for most issues. It shows in the quality of their distribution.
The Zorin devs are somewhat committed to maintaing Zorin 16 until 2025 when its base hits EOL. Moving to Debian would probably involve having to maintain two bases for a period of time. That would definitely increases their workload.
Personally I would like to see it based off of Debian as there is a level of predictability that it offers over Ubuntu.