When comparing Codio vs GitHub Codespaces, the Slant community recommends Codio for most people. In the question“What are the best cloud IDEs?” Codio is ranked 12th while GitHub Codespaces is ranked 18th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Designed to teach programming

Pro Fully functional terminal
Codio gives you full access to a terminal, with all the ubuntu commands. You can use the terminal within the page, or you can access by SSH from your computer.
Pro Emmet
Emmet support for a whole range of features that really boost productivity when working with HTML and CSS. These features include expanding abbreviations into full HTML or CSS as well as some very powerful keyboard shortcuts.
Pro BitBucket integration
It's possible to launch Codio from within BitBucket's repo by adding Codio integration as an add-on.
Pro Server-side environment

Pro Node.js included by default.
Pro Monokai
Includes Monokai style theme by Luigi Maselli.
Pro Preferences are synced
Your Visual Studio local preferences and extensions are saved within GitHub, allowing you to use your configurations on the go.
Pro One-click experience
Designed to make contributing to a repository easier, all it takes to start the cloud IDE is its dedicated button within the repository page.
Pro Visual Studio Codespaces extensions works as-is
If you are a customer for Visual Studio Codespaces, your extension to control GitHub Codespaces will also work and you will be able to use your Visual Studio Code to interact to the Codespace instead of using the Web IDE if need be.
Pro Extensible and configurable
Borrowing from its bigger sister, Visual Studio Codespaces, which is also based on Visual Studio Code, any VS Code extensions work outside the box, no gotchas.
Pro Customizable environments
Environments can be customized in the user-level or the repository using a container declaration file, allowing the environments to be tailored according to the user and the target project
Cons
Con Private projects aren't free
The pricing plan looks too restrictive comparing to other Coding Cloud solutions.
Con Limited to GitHub
As this is a GitHub Product, do not expect it to work with the likes of GitLab or BitBucket. If you want to use third party VCS providers, you might want to use Visual Studio Codespaces instead.
Con Limited to 5 Codespaces instances
GitHub Codespaces currently limits you to 5 concurrent working codespaces. You have to delete another to start another codespace.
Con Early-Access Software
Currently invite-only, expect GitHub Codespaces to have some bugs until its GA release.
