When comparing Processing.js vs Pixi.js, the Slant community recommends Processing.js for most people. In the question“What are the best JavaScript drawing libraries?” Processing.js is ranked 4th while Pixi.js is ranked 12th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Good at creating complex visual effects and filters
Pro Fast rendering of complex scenes
Because Processing doesn't keep track of shape objects it's more efficient than other libraries. Processing can do more complicated effects faster than other libraries. Although this means you have to keep track of more yourself in your code, it also means you have more control over the finer details of how things are rendered.
Pro Cross-platform compatibility
In processing you can write code in both JavaScript and Processing code. This allows you to use existing Processing code on the client side.
Processing code is similar to Java in that it has static typing. This can make more complex calculations more robust, and less likely to cause conflicts.
The library takes a more frame based approach to rendering, so you use drawing functions to draw directly to the frame without objects. This can make it easier to write efficient full frame rendering scenes and post processing effects.
Pro Supports WebGL w/ canvas fallback
Pixi is a WebGL renderer, but can fall back to canvas if WebGL is not supported or turned off.
Pro Will be familiar to ActionScript developers
Pixi.js uses a code structure that's very similar to ActionScript.
Cons
Con Processing.js is now archived, and won't be updated
Con Not a complete solution
Pixi only provides the renderer.