When comparing MS-DOS vs Haiku, the Slant community recommends Haiku for most people. In the question“What is the best laptop OS?” Haiku is ranked 31st while MS-DOS is ranked 62nd.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
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.
Pro Very fast
Pro Beta has been released
After about 6 years since the alpha version, beta has been released on Fri, 2018-09-28. Check here for release notes.
Pro Only need 512mb ram
Pro Stability
Pro Runs perfectly on old Hardware
Cons
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.
Con No one uses it
It's a very niche OS that no one uses.
Con Unfinished
It's still in beta and quite unstable. Making it unsuitable for developing applications of any kind.
Con Language support is terrible
Con Small community
It is important when developing to be familiar with tools that other developers use. You can make any utility in any language you feel like, but if it's in an esoteric language that no one can read targeting a small platform that no one uses, then it was just something you did as a hobbyist, not as a developer.
This is not to say that Haiku isn't a great operating system to hack around on. Just don't delude yourself into thinking you're doing it to get familiar with tools that you need to know to be a better developer.