Chromium OS vs SparkyLinux

Since you only have the browser, you cannot install applications (outside Chrome Apps which are decently protected by their limited API and the Chrome Web Store). This means no harmful virus, and also nearly no way you can screw your system. Everything will just work.

Chromium's system UI uses as little screen space as possible by combining apps and standard web pages into a minimal tab strip: While existing operating systems have web tabs and native applications in two separate strips, Chromium OS combines these, giving access to everything from one strip. The tab is the equivalent of a desktop application's title bar; the frame containing the tabs is a simple mechanism for managing sets of those applications and pages.

Because Chromium OS is designed for users who spend most of their computer time on the Web, it is intended for use in computers with little local storage and fast boot-up times.

You have access to a large user repository, Ubuntu guides can mostly be applied since both are based on Debian.

You have the option for Sparky to be based on Stable or Non-Stable, bringing greater flexibility to user priorities.

Sparky is designed to be lightweight in it's core. It is based on Debian but optimised for old hardware, meaning you can run a full heavy desktop environment on a lightweight foundation, bringing greater performance compared to similar Debian or Ubuntu-based distros.

Any Linux desktop in it's vanilla form can be installed on top of Sparky, whether that be alongside a pre-existing environment, or on top of a basic command line system. Furthermore, the command line system is easy to operate due to Sparky's advanced installer utility, from which you can choose whichever desktop environment you desire, straight from the Debian repositories. Guidance is on their website.