Flatpaks work for me pretty well.

Neither. I exclusively use Nix packages. If I had to pick, AppImage because I can easily extract it to package for Nix :P

The arch repos are enough for me except two softwares so I downloaded them as appimages. Appimages are enough for my small needs.

None of them

None

I'm still trying them out, but if they work as advertised, then AppImages. That's mostly because I use my desktop and laptop pretty much equally, so being able to copy and AppImage from one to the other and keep going would be really handy.

On a similar note, if a computer dies, being able to just copy and paste them to a new computer, or run them from a portable drive would be great.

I don't think I've ever actually found a flatpack in the wild. Not a fan of snaps but have a few appimages that seen to work fine.

Snaps, hell no. I wouldn't touch anything Canonical TBH.

Appimages are very chaotic.

Fkatpaks leave a bunch of trash after uninstalling.

I use Flatpaks, while they are not perfect, they are improving.

I've only used flatpak and I honestly see no reason to try anything else. The only issue I've encountered is that Steam games launched by the Steam flatpak occasionally act strange (sometimes they can't locate graphics drivers or connect to online services).

Snaps. Everyone seems to hate them for ideological reasons rather than practical reasons. But for me, they just work. And if Canonical gets out of line, there's already been proof of concepts of third-party snap repositories, so that's a moot point.

Flatpaks seem like a solution in search of a problem to me. Not everything is a gui app, so not sure why the devs aren't supporting cli apps well. But the biggest problem is that most software I use simply isn't available as flatpaks.

Flatpaks are insecure by design as they don't cryptographically verify their authenticity after download. Snaps too.

Install with a proper package manager that was designed doe security. Most OS package managers are designed with this.