As an example, on my system apt-get
needs to download 3.5 MB to install the IDE geany, while the download size is 100 MB for snap. This is so big and unacceptable! Even the Windows installer of geany is no more than 15.4 MB in size!
What libraries used by a software are included in its snap file? And what are assumed to be already present on the OS? Does a snap file include all the required libraries? If that is the case, why? I see no reason why more than one copy of each specific version of a library, say GTK, should be present on a system.
Maybe I haven't understood the snap system well enough. Maybe the download size of each snap depends on the snaps already installed. For example, maybe if another application installed by snap uses the same version of GTK, the download size for snap installation of geany would be less than 100 MB.
I think you answered your own question. Snaps are bulky because they also include some dependencies, and are thus "self-contained" apps. There are pros and cons.
The reason you would have more than one instance of a library on a system is because there could be different versions required, especially if you're running older apps. I think for newer apps that uses the latest dependencies, this should rarely be an issue.
If you have no dependency issues, there is no real reason to use snaps - this is especially true for servers. For myself, I've had little reason to install snaps over apt packages (also because the snaps I tried was not maintained, and thus had less functionality than the corresponding apt packages).
Correct, Snaps are much bulkier than regular packages because they are an alternative way to distribute and install apps by being self contained by including all their dependencies within themselves.
Advantages of Snaps:
Downsides of Snaps:
What I personally use Snap for
All other instances I would prefer the Ubuntu apt package manager.
Also note that in some cases, if Canonical decides the Snap package is better in all ways than the version of an app you installed via apt, Ubuntu will automatically install the Snap instead without notifying you(!)