Chocolatey NuGet is a open source Machine Package Manager, somewhat like apt-get, but built with Windows in mind.
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Pro Large number of applications/utilities available
Chocolatey has a massive community package repository of installs (more than 4,000 packages), and its open nature allows everyone to contribute more as needed.
Pro Straightforward install process
You can put Chocolatey install commands into your powershell scripts.
Pro Free and open source
Pro Easy to use
Just open powershell and type
choco install firefox to install Firefox, or
choco install java to install Java.
Pro GUI available
There's a package, called ChocolateyGUI that can be installed and lets you use Chocolatey with a UI frontend.
Pro Support and features available for organizations
There is a business edition available for organizations that need more support. The business edition also includes a Package Synchronizer, Package Internalizer, Package Builder, and a host of other features.
Pro Can be extended with PowerShell
Chocolatey allows installing extension packages that add PowerShell functions to your package automation scripts.
Pro Manages the entire software lifecycle
From install to upgrade to uninstall, Chocolatey manages the whole process.
Pro Integrates with almost every configuration management / infrastructure automation / RMM tool
Pro Downloaded files are verified by checksums
Chocolatey requires checksums by default for files downloaded over non-secure locations and highly recommends it for HTTPS/SSL locations. It is moving towards requiring checkums by default for downloading from secure locations.
Pro Builds on technologies you know
Unattended installation and PowerShell.
Pro No crapware
Installs silently without crapware.
Pro Decentralized package sources
Packages can be installed from multiple sources, including private sources.
Pro Upgrade all software with one command
choco upgrade all is like Windows Update for all of your 3rd party software.
Con Unable to easily change your install directory in the free version
In the free version you must know the native installer switches and pass them through with install args. In the paid versions you have a ubiquitous install directory option where Chocolatey determines how to properly pass that to the underlying native installer.
Details on the differences - http://stackoverflow.com/a/19777121
Con Sometimes hard to know which package to install from community package repository
The community repository contains multiple packages with similar names, making it hard to know which one to install. This is of course only related to using Chocolatey with the community repository, and you can look up the number of downloads to see which are the most widely used.