Click packages are isolated, so run in confinement with a "personal" directory and thus cannot provide dependencies to other programs. Intended originally for Ubuntu Mobile/Touch but later for the desktop, they were directed towards user applications because of their bundled dependencies and protected nature (e.g. you could have multiple versions of the same application, all using different libraries and all unaware of each other).
Snappy packages are an iteration of the packaging concept, in that they can provide functions to other packages, and don't have to be confined. They can thus be the basis for system-wide applications/functions as well.
Click packages are isolated, so run in confinement with a "personal" directory and thus cannot provide dependencies to other programs. Intended originally for Ubuntu Mobile/Touch but later for the desktop, they were directed towards user applications because of their bundled dependencies and protected nature (e.g. you could have multiple versions of the same application, all using different libraries and all unaware of each other).
Ref: https://click.readthedocs.io/en/latest/
And the answer to a familiar (to you!) question here: What are Click packages?
Snappy packages are an iteration of the packaging concept, in that they can provide functions to other packages, and don't have to be confined. They can thus be the basis for system-wide applications/functions as well.
Ref: http://www.webupd8.org/2015/04/ubuntu-desktop-to-eventually-switch-to.html