Starling JS vs PlayCanvas

Starling is available for free with code available on GitHub.

Starling is just 12k lines of code and doesn't try to do everything - but what it does, as efficient as possible.

Forum is always active with knowledgeable developers and with lot of inside info, and post mortems.

PlayCanvas has an online editor that lets you build scenes and work with other people in your team in real-time. This is all done through the web browser without having to install any additional software.

Assets and content delivery is very different on a web platform comparing to native. So PlayCanvas challenges best practices to allow developers decide how their content is delivered and in what form.

Async Assets download allows developers to load content as the app goes, instead of asking to download all assets in advance risking users to simply navigate away while staring at loading screens.
Formats for 3D models and textures support covers all the popular tools. And the workflow is as simple as dragging and dropping your files right into the Assets Panel. The cloud will do the rest of the hard work optimizing and converting your files into runtime-friendly and compressed data.

Has an advanced WebGL renderer that runs in the browser.

Lightmaps are an efficient way to deliver lighting to your scenes for a long time. But they come with the cost of large textures. PlayCanvas offers a unique solution for a web platform, it renders lightmaps when an app is loading in runtime.

This is faster than downloading MBs of textures. And it's much more convenient: simply switch your light sources to bake, and static models to be lightmapped, and the engine will do the rest.

PlayCanvas has Feed as homepage for registered users, listing Dev Logs of other developers. This allows to socialize with other developers like yourself in a twitter-like environment.
More to that, there is also an active forum, where developers help each other to solve their challenges.

Developers of PlayCanvas itself are always looking forward to chat and help the community with any problems that may arise.

PlayCanvas lets users integrate physics in their game rather easily, using the powerful Bullet Physics Engine (ammo.js). Should also be noted that the physics engine is delivered as an optional library, so by default being disabled it does not add any extra download size to your apps.

Engine is free for projects under 200MB and with no more than 2 people on a team. The free tier has no engine restrictions.

Tools are totally free too. There are no special limiting features behind any paywalls, and free users have all the features as paid users.

There are no royalties associated with publishing your apps and games - you've made them, you own them.

It is free to publish to playcanvas.com as well, just by one click in Editor.

PlayCanvas lets you build games that run in mobile, desktop browsers, and native mobile apps. PlayCanvas can even make games that can run inside mobile social media and instant messenger clients like Twitter and WhatsApp.

The engine itself weighs just under 150Kb, and it's always challenged to stay small. There is no extra weight that has to be carried with your app, just your assets and scripts in a runtime-friendly compressed form.

This allows users to engage with your content in matter of seconds, and even just under a second on a good connection.

PlayCanvas is fully open source and is under active development.

Real-time link between your launched app and the editor allows the developer to preview and play with their scene without needing to refresh the game after every change in the code to see the updated result.