When comparing Knoppix vs ChromeOS Flex, the Slant community recommends Knoppix for most people. In the question“What are the best Linux distributions for an old machine?” Knoppix is ranked 11th while ChromeOS Flex is ranked 39th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Powerful and lightweight
Pro Lightweight and fast
This is basically just Chrome OS which already runs on Cheap chrome books. It works well for web browsing and file storage on low end computers.
Pro You can try it via bootable USB
Cons
Con Runs off of optical disk by default
You have to enter a special boot option to run Knoppix entirely in RAM.
Con DVD version requires a lot of RAM
Many computers are incapable of loading the whole 4 gigabyte DVD into RAM. There is an older CD version, however.
Con Limited hardware support
There is a list online of about 100 or so computers that officially support Cloud Ready, but it can also work on a laptop not on that list, results may vary.
Con Only really meant for web browsing
To use the software, you need to have a Google account and log in. Because it's meant for web browsing and researching, you won't find software like Steam, Office, Adobe Photoshop, Aftereffects, etc; or even a 3rd party browser other than Google Chrome.
Although there are plenty of alternative web browser online, and in the Chrome Web Store, which is still supported by Chrome OS.