Highcharts provides 20 different types of [charts](http://www.highcharts.com/docs/chart-and-series-types/chart-types) to choose from, and they make it simple to [combine](http://www.highcharts.com/docs/chart-and-series-types/combining-chart-types) chart types.
Ranked in these QuestionsQuestion Ranking
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.
Pro Excellent browser support
Highcharts supports all modern browsers (including IE6 and up), iOS and Android.
Pro Lots of good examples
The site has a selection of good examples that will help you get started quickly.
Pro Good documentation
Very handy with examples and explanations.
Pro Library to support Microsoft .NET
Compatable with .NET framework 4+, can develop graphs from server side for ASP .NETand ASP .NET MVC applications.
Pro Supports multiple Y axes
Important for trend correlation, eg. comparing number of clicks to sale amounts. Not same scales / units.
Con Not a complete solution
Pixi only provides the renderer.
Highcharts is not free for commercial projects, with a starting price of US$590 for Single Developer + Maintenance & Support
Con The examples are not that great
For instance, example's JsFiddle may get stalled when loading.