I was asked this question recently. Everyone likely has an answer: Red Hat Linux, Debian GNU/Linux, Solaris… My answer surprised the questioner: UNIX and UNIX-workalikes. This includes FreeBSD… and Red Hat… and Solaris… and HP-UX… and AIX… and so forth. When I first became interested in UNIX, not one of the aforementioned products existed. First UNIX system I got my hands on briefly was Eunice (look it up 🙂 and the next (a few years later) was Microport System V (for the IBM AT).
Perhaps you might think Solaris is better than Linux – or NetBSD is better than OpenBSD. I suggest it doesn’t matter. Each UNIX (or UNIX-like) environment has its pluses and minuses. Individual choices are personal and enterprise choices are practical – in either case, which is truly better doesn’t matter.
If your enterprise is using Oracle, for example, the choice of which UNIX system you use is dramatically reduced: which system will Oracle support? You won’t be using Oracle on FreeBSD unless you forgo the Oracle maintenance contract. Choices like this continually appear in the enterprise. Perhaps the new version of Red Hat Enterprise Linux has everything you want – but Oracle doesn’t yet support that version.
Alternately, which system you use for your own desktop is a personal choice. Which one is “better” is which one feels better to you. UNIX is, at its heart, unified – that is, it is a single environment – but it provides a wide choice of user interfaces, user programs, and even technical items such as filesystems and virtual memory management schemes. Use whichever one seems better.
What do I use on my personal desktop? Mac OS X. However, in line with the ideas posited above, I’ve just expanded my “desktop” with Synergy, linking my “other” desktop (first Fedora Core 5, now BeleniX with OpenSolaris core) to my Mac OS X desktop. More about Synergy later.
So next time someone tells you what their favorite operating environment is – why not find out what it is they’re so excited about? You might find something exciting yourself.
UNIX Administratosphere 
“So next time someone tells you what their favorite operating environment is – why not find out what it is they’re so excited about? You might find something exciting yourself.”
Yes you are right. One should consider his/her own interest.