SQL Server is to Windows what Oracle is to Unix. Oracle has been around since the 70s or early 80s, and it carries a lot of legacy pre-ANSI SQL baggage. There is a much larger body of proprietary knowledge to learn, a lot more switches to tweak, and the impression I get is that there are more Oracle developers but fewer Oracle experts.

On the other hand, SQL Server is newer and will deprecate features that become obsolete (a good thing in my opinion), making it a much cleaner and easier to learn. Go to Barnes & Noble or Borders, browse the books on Oracle 11g and SQL Server 2008, then decide for yourself which speaks to you.