No strong opinion on snaps one way or the other, I haven’t used them too much.

With flatpak, my own opinions are mixed. On one hand, I do like the fact that they come with all their necessary dependencies, so you’re not stuck in dependency hell with native package managers, especially if for some reason a package ends up in the native repos that doesn’t have its dependencies, or at least the needed versions of them, also there. Using the distro I’m running now (KDE Neon), that’s happening at least with package versions a bit too often for my liking, even with KDE’s own apps. I also like, then, that with flatpak you can run more recent versions of apps than you could using the native packages.

The downsides I’ve run into, though, are firstly with permissions, it’s trickier than usual to make sure flatpaks have all the permissions they need to run the way you want them to, especially if you’re not sure exactly what permissions they need. This is made easier with Flatseal, but then I’m sitting there sometimes playing Whac-A-Mole with Flatseal settings trying to find the right combination. I’m also not a fan of some flatpaks still not correctly following the system theme, making them stand out and look awkward, and lastly, I will try to stick with native apps if I can because the space on my system is somewhat limited, and including all the dependencies with flatpaks makes them use up a lot more space than the native packages.