SnapCraft or known as "Snap", is a Distribution-agnostic Linux apps packaging repository and tool. It emmphasizes security and portability in mind.
Ranked in these QuestionsQuestion Ranking
Pro Built in sandboxing
Snapcraft is designed with isolation and security in mind. All system and library definitions are defined from the core snap package instead of the host's, adding a security layer. Snaps are also designed not to arbitrarily access the host FS unless the snap is a classic snap.
Pro Auto-updates periodically
Snaps are designed to auto-update. You can trigger the update, however, with snap refresh.
Pro SnapCraft is maintained regularly
the default marketplace - SnapCraft.io, is maintained regularly with fresh new software. You can find many development tools and software from SnapCrafters or from the publishers of the software themselves.
Pro Integration with Store applications
GNOME Software and Ubuntu Software has a tight integration to Snaps, just like Flatpak, making installing the apps easier.
Con Hard to use external "stores"
SnapCraft allows you to set up a "store" (repository) but it's very difficult to add.
Con Some distributions has outdated version of snapd
Distributions like Fedora might have a outdated version of snapd. However, this is not a case to be worried as some distributions will update when notified of a new release.
Con Requires a one-time installation of the core snap package
The Core snap package is the heart of Snaps. This is always a required installation for first time Snap installs as it is a price you pay for using Snaps and its security advantages. However, this snap package is very small (around 65MB) so it should not worry you.
Con Might have a mismatch with your GTK/KDE theming
As Snaps don't have access to your system preferences, they will use the default settings or whatever was on the core snap package. This can be rectified by installing the gtk-themes-common package.
Con Slow startup for first-time init
It may take time for the snaps to load when launched first-time, succeeding inits will be faster.