When comparing FlashDevelop vs IntelliJ IDEA, the Slant community recommends IntelliJ IDEA for most people. In the question“What are the best Haxe IDEs?” IntelliJ IDEA is ranked 2nd while FlashDevelop is ranked 6th. The most important reason people chose IntelliJ IDEA is:
IDEA places an emphasis in safe refactoring, offering a [variety of features](https://www.jetbrains.com/idea/features/refactoring.html) to make this possible for a variety of languages. These features include safe delete, type migration and replacing method code duplicates.
Ranked in these QuestionsQuestion Ranking
FlashDevelop comes without any cost.
Pro Good code completion
FlashDevelop's code completion is pretty good.
Pro Haxe development support
FlashDevelop has first-class support for Haxe development, the open source toolkit based on a modern programming language and cross-platform library.
Pro Excellent support for Actionscript 2 and 3 (Flash)
Although everyone claims Flash is dead, it's still quite useful for game developers due to its rapid compile and run times, as well as its great debugging functionality with FlashDevelop.
Pro Good number of project templates
While it's project template system is not the best compared to it's competitors, it still is decent and is a good way to generate some boilerplate code.
Pro XML/HTML completion
FlashDevelop has XML/HTML completion aside from code completion.
Pro .NET Framework 2.0 application
It's windows only, but has tremendous support from plugin developers and a dedicated team that's been developing it for close to 10 years.
Pro Source-control support (svn, git, mercurial)
Pro Great debugging
FlashDevelop provides very efficient debugging features.
Pro Supports Zen-coding for HTML
This is very useful for carrying out high-speed HTML coding and editing.
Pro SWF/SWC exploration
Pro Great project compilation
FlashDevelop facilitates project compilation.
Pro Decent code generation
Although the code generation can't really be called top-notch, it's decent and sufficient for most developers.
Pro Smart refactorings
IDEA places an emphasis in safe refactoring, offering a variety of features to make this possible for a variety of languages.
These features include safe delete, type migration and replacing method code duplicates.
Pro Fast and smart contextual assistance
Uses a fast indexing technique to provide contextual hints (auto-completion, available object members, import suggestions).
On-the-fly code analysis to detect errors and propose refactorization.
Pro Android support, JavaEE support, etc
A very complete development environment support.
Pro Lots of plugins
Many plugins are available for almost any task a developer may need to cover. Plugins are developed by Jetbrains themselves or by 3rd parties through the SDK available for writing them.
Pro Stable and robust
IntelliJ IDEA hardly ever crashes or has any issues that plague other Java IDEs like file corruption or slowness.
Pro Support for many languages
IntelliJ supports many languages besides Java, some of these are: golang, Scala, Clojure, Groovy, Bash, etc.
Pro Intuitive and slick UI
IDEA has a clean, intuitive interface with some customization available (such as the Darcula theme).
Pro Clear and detailed documentation
The documentation is exhaustive, easy to navigate, and clearly worded.
Pro Free version available
There is a free community edition (open source) and an ultimate edition, which you can compare here.
The ultimate edition is available for free for one year for students but must be registered through an .edu e-mail account.
Pro Many convenient features
These simplify the daily work, e.g. copy/cut a whole line without the need to select it.
Pro Very powerful debugger
With ability to step into a certain part of a large method invocation (Shift+F7), drop frame, executing code snippets, showing method return values, etc.
Pro Buit-in Git support
Pro Gradle support
Con Windows only
FlashDevelop is for Windows only, and it's not cross-platform either.
Con Haxe debugging is in its infancy
Although FlashDevelop supports breakpoint debugging on Flashplayers, native Haxe applications (C++) can't be easily debugged within FlashDevelop.
Con Uses too much RAM
Con Slow startup
Startup can be slow deepending on system configuration
Con Bugs are not solved as often as they should
They are more interested in adding new features or issuing new versions than solving bugs.
Con Cannot open multiple projects in the same window
Con Built with closed source components
The version with full features is not opensource. Parts of the code are under apache licence though.
Con Standard hotkeys behave differently
Seems like hotkeys assignment in Idea has no logical consistency.
Like «F3» is usually next match, «Ctrl+W» - close tab, etc — they map to some different action by default.
There is a good effort in making the IDE friendly for immigrants from other products: there are options to use hotkeys from Eclipse, and even emacs. But these mappings are very incomplete. And help pages do not take this remapping into account, rather mentioning the standard hotkeys.
So, people coming from other IDEs/editors are doomed to using mouse and context menus (which are rather big and complex).
Con Lack of plugins
IntelliJ supports a very small amount of plugins. Although these are 'quality approved', many features are missing and can't be implemented because of that.