Solaris is not open source, it was created by Sun Microsystems, and it is now owned by Oracle...And all the implied baggage that entails. Oracle is not terribly friendly to open source or free software, hence their stance on OpenOffice.org, and mysql. They allowed OOO to languish to the point of driving developers away from it, which is why it was forked into LibreOffice. They finally washed their hands of it and gave it to the Apache foundation. They have gone out of their way to obfuscate security patches in mysql, and their first action with Solaris was to eliminate the free versions, causing another fork. There are, as someone stated, projects like Illumos, which are forks of the last free version of Solaris.
In operation, Solaris has always been slower than Linux, even on native Sparc hardware. Many things in the OS are either crufty non-GNU tools, such as tar, which lacks many of the options that GNU tar has (though there are sites like
sunfreeware.com), or they are different for the sake of being different. Like other commercial unixes, they had to do things differently to make them unique, so patching is much more painful than a Debian or RedHat or FreeBSD box.
FreeBSD has, arguably, a better package system in the ports tree. Ports is/can be configured to do source-based installs of applications. It also has ZFS, which is arguably the best filesystem available, as long as you have tons of memory. I don't have a lot of experience with FreeBSD, though I am starting to experiment with it. FreeBSD is also open source, though not GPL. It uses the BSD license, which basically states that you can do anything you want to with the software.
Personally, I would either stick with Linux or try FreeBSD.
And I managed to do this entire email without calling it "Slowaris" :)