When comparing ShiftEdit vs Google Cloud Shell, the Slant community recommends ShiftEdit for most people. In the question“What are the best cloud IDEs?” ShiftEdit is ranked 7th while Google Cloud Shell is ranked 10th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Low cost, high quality

Pro Revision control
Pro Syntax checking
Highlights syntax errors and automatically fix some errors
Pro Supports multiple file access points
Access files from FTP, SFTP, WebDAV, Dropbox, Google Drive or Amazon S3
Pro Supports autocomplete
Code completion for HTML tags, CSS and PHP code assist
Pro SSH support
Allows connecting directly to a server and run commands on that server.

Pro Good Customer Support
Help requests get answered quickly and successfully.
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 Expensive
Con Not user friendly
Con Non free/libre (proprietary)
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.
