Firefox auto-updates with the snap version, whereas it doesn’t with most package manager versions. So if it updates while you’re using it, it won’t let you open new tabs without restarting it (Firefox, not the machine), which can interrupt your workflow. On other distros, that only happens when installing updates manually, which isn’t an issue because you’re aware of it.
This is second hand info though since I don’t use Ubuntu, so YMMV.