DPKG is the core of package management in Debian-based Linux distributions. It has multiple front ends like apt or aptitude that extend dpkg's usability and features.
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Pro Great multiarch support
DKPG has one of the best multiarch support you can easily add new architectures with dpkg --add-architecture $ARCH to install foreign architectures.
Pro Follows the UNIX philosophy
DPKG and it frontends follow strictly the UNIX philosophy that one package should do one thing well.
Dpkg: does simple package management
APT and aptitude : adds repository and dependency tracking
debconf: does configuration
synaptic: allows mouse interaction to all apt/aptitude options
Pro De facto package manager / widely used
Due the popularity of Ubuntu, Debian and Linux Mint it is almost certain that you find the package you want as a pre-built deb package.
Pro Very easy to create packages
There are plenty of helpers to easily create packages.
You just need to create 5 files: source/format, compat, rules, control & changelog and run dpkg-buildpackage.
Pro Standard archives
Deb packages are simple ar archives with additional tar, lzma, bzip, gzip support.
DPKG isn't as bloated as other package managers since it is only made for local package management.
Pro Plenty of frontends
You can use apt, aptitude, cupt, debdelta or apt-build on the terminal.
Pro User interaction
It is possible to interact/ask questions to all pre and post install scripts. This makes it possibe to add questions for package configuration or to display EULA/License screens that have to be accepted before installation.
Pro You can create deb packages on almost all linux distributions
This makes maintenance and support easy.
Con Does not work well with packagekit
Since packagekit was developed with rpm in mind it does not support all dpkg features.
Con Package creation needs more than one file
A debian package needs at least the following files to build it with debhelper
debian/source/format - deb format
debian/changelog - changelog file with version number and dae etc.
debian/compat - debian package version
debian/control - package information, dependencies & co
debian/copyright - license information
debian/rules - the make file to build the package
However the really important files are control, changelog and rules all other are generic.