Ranked in these QuestionsQuestion Ranking
Pro CoffeeScript and SCSS support
Pro Allows collaborating on code
JSFiddle makes it easy to save the code snippets and send the link to others who can view and edit the code.
Pro Supports a wide variety of frameworks and extensions
JSFiddle can switch to selection of frameworks and extensions including jQuery, AngularJS, ReactiveJS, D3 simply from a dropdown.
Pro Courses taught by industry professionals
Pro All courses are self-paced
Courses are always made available which means there is no waiting for the specific course you want to run. You can work through the courses as fast or as slow as you want.
Pro Offers Nanodegrees
Udacity offers a few different Nanodegrees which provide access to various different courses, project reviews and coaching support for $200/month.
Current options include Front End Web Developer, Data Analyst and Android Developer. See the full list here.
Pro Courses are easy to understand
Pro Actual feedback on coding projects
You get actual feedback from developers on your code, which is useful. Yes having your sites/apps do what it is supposed to do is important, but you need feedback to learn industry standards/best practices and other gotchas that are much harder to learn on your own.
Con Not actually an IDE
JSFiddle is not actually an IDE and is only suitable for small blocks of code.
Con Non free/libre (proprietary)
Con Nanodegrees are expensive
Udacity is quite expensive at $200/month if you want to do a nanodegree.