Well, Solaris is SVR4 based UNIX. So your question becomes whether SVR4 is better or BSD is better. Personally, I don't have a preference. Both have pros and cons. Solaris, HPUX etc are SVR4 based, most Linux are kind of BSD based. With Solaris goes open source and with Solaris 10's new feature such as ZFS, zone, D-trace, SMF with self-healing and improved performance and security, it continues to be very competitive.