On older hardware – BAD. Snaps gobble up scarce resources on older hardware. On newer hardware with a zillion and twelve terrabyres of RAM and storage space, not that big a deal, but still a lot less efficient than good ol’ tried-and-true .deb or .rpm packages on Linux.
So why would Ubuntu make snap packaging the default in their distro and it’s flavors? Because it relieves them of the burden of having to maintain all those modified .debs in huge repositories with multiple packagers and maintainers. The burden shifts to the writers and vendors of the software instead of maintainers at Canonical / the Ubuntu family. Saving lots of work and lots of money.
The problem is, though, that updates to software for the operating system can mess up the snap applications, and vice versa! With repositories and maintainers, those problems are avoided most of the time. That’s prob’ly why Linux Mint said “no freaking way” to snaps as the default on Linux Mint. It’s a distro for newcomers to Linux, and having it break all the time because one independent package out of thousands of them borks the system is enough to drive users back to proprietary OSes and imagine, as before, that Linux is “just for geeks and for servers.”
This video is kinda long, but it’s good! More info about snaps, and why they’re unpopular with developers of even Ubuntu-based derivative distros: