When comparing Eclipse Che vs Google Cloud Shell, the Slant community recommends Eclipse Che for most people. In the question“What are the best cloud IDEs?” Eclipse Che is ranked 8th while Google Cloud Shell is ranked 10th. The most important reason people chose Eclipse Che is:
Built-in terminal with root access so you can make changes to your running machines. Being able to SSH into the workspace so you can use a desktop IDE is handy.
Specs
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Pros

Pro SSH + terminal
Built-in terminal with root access so you can make changes to your running machines. Being able to SSH into the workspace so you can use a desktop IDE is handy.

Pro Custom commands
You can package up custom commands with your workspace and then use them (or share them) with everyone else.

Pro Docker runtimes
You can choose from pre-configured environments for Java, Javascript, C++, PHP, C#, etc., or you can define your own by dropping in a Dockerfile - makes it easy for simple and complex projects.
Pro GIT and SVN VCS support
Projects can be easily imported from any Git or Svn repository hosting service.
Pro Reproducible environment

Pro Portable workspaces
The workspace in Che includes project sources, IDE and the runtime. So if you hand your Che workspace definition to another user and they execute it they will get everything they need to build, run and debug the project.
Also the runtime is in a Docker container so it will work even if the second user is on a different OS than the original user who shared their workspace with them.

Pro Previews
Che does a nice job to automatically map the service:port running in the Docker container (e.g. tomcat on 8080) to the Docker port it actually uses (something in the ephemeral range). You never need to figure that out - it's just made available when you run your server.
Pro Merge tool for VCS

Pro Open-source
Pro Inexpensive
Google Cloud Shell is free for Google Cloud Platform customers.
Pro Already has Google Cloud SDK and other tooling installed
Thus eliminating a setup step for interacting with Google Cloud.
Pro Already provisioned with Google Application Default Credentials
This makes it easier to run/test code that interacts with Google APIs.
Pro VM is always up-to-date, making it more secure
Because the VM image is managed by Google and either provided entirely by Google or configured by a Dockerfile (which is regularly rebuilt), packages are far more likely to be kept up-to-date with the last patches and security fixes compared with Cloud IDEs that give you your own VM and make you, yourself, in charge of applying updates.
Pro Supports multiple open files at the same time
One can split the screen and edit two files at once, making it easy to edit one file while consulting the contents of some other file.
Pro Supports editor and terminal in the same screen
This makes it easy to run commands while editing files at the same time.
Pro Built-in integration with tmux
Pro Supports "Boost Mode"
Allowing you to provision a more powerful instance when necessary.
Pro Supports custom software packages via a Dockerfile configuring the Cloud Shell image
With Cloud Shell custom environments (an early access feature), it is possible to specify a "Dockerfile" to specify a custom VM image to use for the Cloud Shell environment. This Dockerfile can be used to install packages with apt-get, npm, pip, etc. globally.
Pro Includes Eclipse Orion IDE already configured
Eclipse Orion can be difficult to setup/configure if creating a do-it-yourself VM running Eclipse. This makes it easier to have a working IDE.
Cons
Con Slow runtime
Online IDE is much slower than desktop one.
Con Ephemeral Disk
Software installed globally as root (such as via "sudo apt-get install..." ) can be lost when restarting Cloud Shell; any software that needs to be persistent has to be installed in the user directory (or made part of the Docker image for the custom Cloud Shell image).
Con Minimal UI
Cloud Shell's editor is not as featureful as some alternatives.
