It depends on whose marketing department you contact .
It also depends on what you want to do. Solaris is intended primarily for Sun hardware and they provide high-performance *n*x functionality.
Unix, is AFAIK
only available from SCO, and SCO's busy alienating everyone in sight except for maybe Microsoft.
Linux is free and very popular, but SCO's making a lot of CEOs nervous about Linux on account of their legal maneuverings.
Then there's BSD which already won lawsuits about who owned the property. Although SCO may attack them next week, if the events of the past few months are any guide.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.