Qubes OS
Qubes OS is a free and open-source, security-oriented operating system for single-user desktop computing. Qubes OS leverages Xen-based virtualization to allow for the creation and management of isolated compartments called qubes.
VS
antiX
antiX is a fast, lightweight and easy-to-install Linux live CD distribution based on Debian's "Stable" branch for x86 compatible systems. antiX offers users the "antiX Magic" in an environment suitable for old computers.