Difference between .pkg and .dmg file?

*.dmg is a disk image, and a *.pkg is sort of like a zipped file.
I don't know the advantages to either of them, though.

DMG:
* Disk image format, like ISO, etc...
* Is not an installer, just a way to store files.
* Supports encryption, password protection and compression.
* Single file (ideal for distribution).

PKG:
* Installer package. Can install files to different locations, etc...
* Support compression.
* Is just a folder, with multiple files inside (just like .app). So it is not suited for distribution.


More information:
http://en.wikipedia.org/wiki/.dmg
http://en.wikipedia.org/wiki/Installer_(Mac_OS_X)