Linux on a USB/CD

Booting an operating system on a flash drive or cd is good because its really fast and nothing saves on the OS. Which means that no one can tell what you did while you ran the OS. Another reason is because you can try an operating system that you dont know if you like or not and just not have to install it you can try it out. A reason why its not a good idea is because it might go slower and you might have to buy a flash drive to fit the operating system on it. So theres the good and bad of an OS on a flash drive or a cd.