I have become a fan of solaris-intel over the past year. That said, I disagree with all of your bullet points about why Solaris is a better OS.
At my firm, we have many solaris-intel servers running our service. We use solaris-SPARC for all the databases.
Our primary reasons for using Solaris are vendor support, maturity, and scalability.
All vendors we deal with provide Solaris versions of their products. Most of these vendors support Solaris-intel, and most of those support or plan to support Linux.
Solaris' threading is a strong point. It's more mature than Linux threads, and more robust.
It's important to note that the "lxrun"
program that runs Linux binaries doesn't support threading. Almost all enterprise class programs these days rely on threading, so that makes Linux versions of these programs unusable on Solaris, despite what
Sun may claim.
Solaris scales very well to many processors and several GB of RAM. Vendor support for storage arrays and other accessories is strong.
We heavily modified the standard Solaris install using various techniques, such as
Titan, and then we performed our own security audit. Our primary means of securing the Solaris servers is shutting off all the network services. Almost all of our Solaris servers are behind firewalls in any case. We have staff that monitor BugTraq and other lists and immediately apply patches or workarounds in response to problems. (you should plan on this no matter what OS you decide to run.)
The reason for solaris-intel instead of SPARC is cost; we chose to implement our system using many cheap Pentium boxes instead of a few heavy SPARC machines. Solaris-intel for databases didn't work out because most database vendors appear to focus on the SPARC platform. Any DB problems we had were generally met with "use a SPARC."
I'm not sure what you mean by "different versions", or the "database system". It appears you're focusing on the add on software you can get with certain OS's. Most enterprise UNIX vendors provide all sorts of software to manage users and filesystems and the like. I personally think that Linux has better precompiled software availability than Solaris, although you can find a lot of good precompiled Solaris software at
www.sunfreeware.com. This precompiled stuff is okay if you're just using Solaris as a workstation, but for a production environment you should build everything you don't buy from source.
I haven't used anything that Sun provides above and beyond Solaris + bintools. I just use the core OS. For most enterprise environments, I think you'll find this is the case. The extra "gravy" is generally for people that intend to use Solaris in a workstation context.
For all the praise I heap on it, solaris-intel is a beleaguered platform that is often supported only begrudgingly by vendors. You may need to negotiate with vendors to keep solaris-intel versions alive, and be prepared to buy some SPARC machines for vendors who only provide SPARC builds.