When comparing Eclipse vs Code::Blocks, the Slant community recommends Code::Blocks for most people. In the question“What are the best Arduino IDE alternatives?” Code::Blocks is ranked 1st while Eclipse is ranked 7th.
Ranked in these QuestionsQuestion Ranking
Pro Large selection of plugins
Eclipse has a large and active community, which has resulted in a wide variety of plugins.
Pro Fast compiler
Eclipse uses a custom compiler (which can also be used outside of Eclipse), which is often faster than the normal Java Compiler, especially for incremental compilation.
Pro Free and open source
Eclipse is an open source project and free to use.
Pro Highly customizable
Thanks to the large variety of plugins and various configuration options, Eclipse is very customizable.
Pro Multiple languages - one IDE
Pro Good refactoring tools
Pro Great debugger
Shows threads, concurrency locks, and conditional breakpoints.
Pro Good font rendering
Because Eclipse is based on SWT, it uses the native font rendering and thus looks better than other IDEs on some Linux systems, where the Java font rendering is not optimal.
Pro Gives good perspectives on your project
The concept of perspectives is outstanding. It puts right tools at your fingertips, keeping the tools you currently don't need out from the workbench. For example, in VCS perspective it's all about versions and branches. In debug perspective it's all about state.
In java ee project it can show http endpoints in a very accessible manner.
Pro Faster than any other Java IDE
Fast, suitable for big projects, customizable, supports UML, many programming languages, plugins, and widgets vs NetBeans and JDeveloper. Support for Workspaces and Perspectives. Long term tested, free of charge, vs IntelliJ IDEA.
Pro Dark theme improved!
Pro Easy to use
Pro Simple Library import
Con UI can be confusing
There's an overly abundant presence of menus, this forces you to constantly click around the different menu structures; foreign ideas, like Views and Perspectives; strange menu choices, like configure settings located in Windows menu->Preferences.
Con Plugins can be unstable
Though there are plenty of plugins to choose from, they aren't always reliable. Some aren't maintained, bug fixes can be slow, and you may need to download plugins from multiple sources.
Con Lack of plugins with good user interfaces
Many Eclipse plugins are extremely confusing, with UIs that are even less consistent than Eclipse itself.
Con Tends to be slow and lags a lot
Con Poor language support via plugins
Eclipse supports other languages with a huge amount of plugins. Many languages have their own distribution, but multi-language is hard to exist in one project. Like Scala, there is no official support from Eclipse for this language. If Eclipse gets an update, languages such as these will not.
Con Newer versions are getting less stable
Eclipse 4 Neon randomly hangs. For example, during installing new software.
Con Some old bugs don't get fixed
E.g. change a parameter name to the same as a field - the field will not be prefixed with "this." like in IDEA.
Con Not very feature rich
By default it's not much more than "What if Gedit had a compiler and a terminal built in?" (or: "What if Notepad had colour coding, auto indents, file structure, a compiler and a terminal built in?")
There are far more professional IDEs out there. This one is much too basic for any efficient use.
Con Slow navigation using mouse
In most IDE's, you can "goto declaration"/"implementation" by holding CTRL and left-clicking on an identifier or include directory. This does not work in Code::Blocks no matter what settings you have. Right-clicking will bring-up a menu that includes these "goto" options, but it's not instant and you'll be slowed down immensely depending on how often you have to do it.
Con Can get quite slow and doesn't look all that good
Con Setting up dark theme requires using system's own gui toolkit
Con Lots of functionality is encountered only in plugins
You can't change keyboard shortcuts, neither share themes with vanilla codeblocks, for example.