Many people think SQL Server is very easy so companies don't pay much to SQL-Server DBA. For Oracle database, it is just opposite.
Anoth thing is: if you are not working with Oracle database, it will be hard to prepare for Oracle OCP.
IMHO, there should be no comparison between the two. Sql Server is a kid database and it will take time for him to even try to catch Oracle. I don't think people who do MCSE with two optional exams of Sql Server, become DBAs of any kind. and moreover there are massive amount of braindumps available for Sql Server (M$) exams, which makes it trivial to achieve. MCDBA is nowhere close to OCP DBA. So go for value, go for Oracle.