My opinion is definitely slanted since I earn my living with SQL Server and have only used Oracle in an academic environment, so I have vastly more experience with SQL Server than Oracle.

But, having experience with both, I will join the majority and say "It depends". In the vast majority of cases, I would take SQL Server in a heart beat. It is easier to use, easier to administer, and has vastly better tools that come with it. I would even happily toss the tools that come with SQL Server against the best tools you can buy for Oracle in most projects. It is also easier to write applications for. (As a disclaimer again, I have more experience in SQL Server, but I have used and written code for both).

While I would say SQL Server would win in most cases, there are 3 areas where I would pick Oracle:

1. Cross platform development since Oracle is available with very few differences on both Windows and Unix.

2. Scaling out. SQL Server has very limited ability to scale out right now, where Oracle is very robust there. I'm hoping SQL Server will catch up soon.

3. If it is necessary to maintain legacy applications already written in Oracle, (or legacy employees already trained in Oracle).