When comparing Haiku vs RebornOS, the Slant community recommends RebornOS for most people. In the question“What is the best desktop OS?” RebornOS is ranked 22nd while Haiku is ranked 30th.
Ranked in these QuestionsQuestion Ranking
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 Runs perfectly on old Hardware
Pro Antergos with more desktops
Pro Good Repo
Reborn's dedicated repo has some extra packages that are difficult to find elsewhere, in addition to the official Arch repos, community repos, and the AUR.
Pro Highly and Easily Configurable
You can easily choose from a list of browsers, desktops, office suites, etc, all from the installer.
Con No one uses it
It's a very niche OS that no one uses.
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.
It's still in beta and quite unstable. Making it unsuitable for developing applications of any kind.
Con UI quite different to other OSes
Crashes every time when trying to install.
Doesn't even install it in virtualbox or VMWare.