Beyond the complaints about Canonical's hostility to Flatpak and other formats, but the real risk snap poses is that Canonical has a lot of control over the snap store, and lack of integration with distros beyond Ubuntu.
There's a vague promise of "new stores" and better integration with other distros but Flatpak is a truly open technology that gives you the option to install apps from ANY source and other distros are collaborating to improve it.