I've looked at moving to the snap before but last I heard there's no way to import your current profile? And netflix doesn't work? If those two things are fixed I'd happily change over!
Netflix for me works fine. You just need to tick the 'Play DRM content' setting.
My personal reason to use the snap is because it limits access to the home directory. So I can disconnect my home directory, camera and microphone and have a second layer of confidence that my browser won't leak any personal data.
That and it avoids Firefox leaking config files in my home directory.
If I want to upload a file, I simply move the file into a Downloads folder in it's SNAP home directory. This way, Im in control of what the browser can access.
For the former, I would imagine `rsync -Pav $whatever_old_ff_profile/ $HOME/snap/firefox/whatever/` would do that, since AFAIK snaps store user-specific persistent state outside of privileged directories
The alternative, and likely why no one has applied a great deal of pressure to that workflow, is to use the Firefox Sync account they've been pushing so hard
They're usually pretty quick, as in nearly as quick as rolling releases (and sometimes faster). Sure, they're not as fast as Mozilla, but usually it's out within a day or so if release, often quicker.
