When comparing Processing.js vs GraphicsJS, 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 GraphicsJS is ranked 10th.
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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 Powerful line drawing
Not only Bezier curves but also any lines, shapes, arcs, etc. out-of-the-box.
Pro Convenient API
Clear and concise API with chaining support.
Pro Virtual DOM
Rapid drawing. Only what is necessary is drawn.
Pro Has its own transformation engine
No need to use embarrassing in-browser transformations.
Pro Legacy browser support
IE6+.
Pro Smart layering system
With z-index.
Pro Rich text features
Multiline text support, text measurement, wrap, indent, spacing, align, etc.
Pro Full accessibility (Section 508)
Pro Events support
All browser events are dispatched in the same way in virtual DOM structure also.