When comparing Tails vs MS-DOS, the Slant community recommends Tails for most people. In the question“What is the best laptop OS?” Tails is ranked 34th while MS-DOS is ranked 62nd.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Privacy focused
Pro Has TOR built-in
Use the Internet anonymously and circumvent censorship; all connections to the Internet are forced to go through the Tor network.
Pro Easy to use with an USB key
Pro Use old editor Edit
The grandfather of Notepad, very easy to use, hassle-free text editor.
Pro Brings back memories to older developers
Pro Best OS to run QBASIC on
While QBASIC works on newer operating systems, such as Windows 95 and Windows 98, it was designed for and runs best on MS-DOS.
Cons
Con Not for daily use
Tails is a privacy focused Linux distro. The updates that you will receive are only for improving privacy and not for improving user experience.
Con You can't install it to a hard drive
Con Saved states are not present for security
For security reasons, saved states are not supported in Tails. Files can be stored in a separate, persistent volume which must be accessed with a root password. Personal settings (e.g. -- keyboard layout, window settings, etc.) are not saved persistently across reboots. This can be a hindrance for anyone not using English as their language, or not using a QWERTY keyboard layout.
Con Only GNOME desktop environment
Con Slow internet
Tails uses the TOR network and as a result the internet on your computer will be very slow.
Con Not a modern OS
If you need to know how to run legacy software that will run on DOS (crazier things have happened, there's probably still some ancient, leviathan, software out there that requires it), go for it. Otherwise you're practicing skills that are out of date and are using an operating system that is woefully insecure.
Con Literally horrible
MS-DOS is terrible -- just read about real mode. It was an almost decent solution for its time, but not anymore.
Con Way too simple
A stripped down version of Unix, some commands just got renamed and advanced options removed.
Con Dead
Ended in the 21st century.
Con No internet support
Using Internet with MS-DOS is not trivial.