TBH, I prefer appimage over flatpaks because appimages are easy to store and backup.
They also tend to not autoupdate, which is good for security (autoupdates are a conduit for a malicious party to push out malicious updates) and making sure you get to keep the version you want (in case a free, open source program gets acquired by some shitty company who then decides to put telemetry and paywalls in a update).