When comparing Duality vs GameSalad, the Slant community recommends Duality for most people. In the question“What are the best 2D game engines?” Duality is ranked 30th while GameSalad is ranked 64th. The most important reason people chose Duality is:
The full source code is available on GitHub, where the framework is actively developed. All of the editor, core and plugin code is written in C#.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Open source
The full source code is available on GitHub, where the framework is actively developed. All of the editor, core and plugin code is written in C#.

Pro Great editor
Duality includes a powerful visual editing system that can be used for previewing, integrating, editing and testing game content.

Pro Live reload of code and assets

Pro Very extensible
Because both Core and Editor are completely plugin-based, Duality not only incorporates a clean and modular design, but is also very extensible - even if it wasn't Open Source. In fact, most of the standard editing capabilities comes in form of Editor plugins.

Pro Built-in physics and lighting

Pro Friendly to version control systems
It can be configured to serialize all data in a text-based format, which has been structurally optimized for version control systems.

Pro Used in commercial projects
It has been used in a production environment without burning the place to the ground. Supposedly artist-proof editor workflow with an API for tailoring the system to fit your team.

Pro Cross-Platform
Pro No-code editor
Pro Has a Windows(.exe) version on par with Mac
The Windows version is now upto date with all the features of its Mac sibling.
Pro Multiple publishing platforms
Can create and publish games for iOS, Macintosh desktop and laptop computers, Android, Kindle, Amazon FireTV and FireTV Stick, Windows 8 and Tizen devices.
Pro Gamepad support
Gamepad support is available as of 0.13.3.
Pro Free standalone viewer app allows instant, live mobile device testing
The GameSalad Viewer is a free app available for iOS, Android and Kindle. Once installed on your mobile devices, you can deploy and test your GameSalad games live on any mobile device running the Viewer that is on the same local network as your dev computer.
This even allows Windows users to test their games on iOS devices without a Mac device and without any complicated code signing or provisioning profiles.
And, you can even take your games with you -- once loaded onto your mobile device, a history option caches recent games on your device without any connection to the dev computer.
Pro Allows you to focus on the logic rather than code
Since the user mainly uses menu options there is very little code needed to be keyed in. This makes the code very easy to read and understand.
Hence there are many help videos on youtube
Pro Extensive community of seasoned professionals for support
Extensive community of seasoned professionals in all disciplines (graphics, game design, animation, physics, music, video production, marketing, etc.) producing tutorials, videos, publishing tips, free templates and who are willing to answer forum questions and help newcomers.
Pro Powerful expression editor and functions
Allows you to create expressions on par with LUA (it's back end-language).
Pro Custom collision shapes with JSON support
Allows you to import JSON data for custom collision shapes to use with Gamesalad's implementation of Box2d physics.
Pro Easy to publish
Software prepares your app so you can just send it to Apple. All my games are reviewed with no problems.

Pro Drag and drop editor
The drag and drop editor makes GameSalad very easy to use, no programming experience needed.
Pro Great engine
Very quick to learn and great for making games. Community is very open and helpful.
Cons
Con Visual Studio required
To have possibility for scripting you have to download entire Visual Studio and spend 10 GB of free space
Con Requires windows for development
Con Bad editor
There is no scene zoom, search boxes, or snap to grid. There is also no ability to focus view on the actor or use folders for file structure.
Con Expensive compare with others
There is no free version any more and it is very expensive compared with other engines.
Con Poor editor performance
Especially when you're working on a big project.
Con No scripting language or SDK
If a needed behavior is not supplied by GameSalad, there's no way to add it.
Con Product is suffering - Lacking company leadership and no voice from corporate
Some customers are currently in a holding pattern from the lack of support and messaging from GS corporate. GS is currently unstable and developers are waiting for another update that has been going on from 2015.
No word or message from GS corporate about timeframes or deliverables.
You can read the ongoing discussion here.
Con Product is in Limbo - company is lacking developers
Con Doesn't support Windows platform (*.exe)
Doesn't support Windows platform (*.exe)
