I don't really think looking at it in which is better or worse has any benefit. There are places where SQL Server is a good fit and there are places where Oracle or any other DBMS is good fit. Base it own what you need and your environment. Both products can and do support vast amounts of data.
@Shawn_Melton brings up a good point. You need to use the version that best meets your needs. If you are fortunate that your application supports both and it is purely a choice of buy Oracle or MSSQL, then I would go with MSSQL. MSSQL is prices per CPU slot not per core like Oracle so your overall cost is much less. Also with MSSQL you have a much better SQL Community. I wrote a blog about some of the free training opportunities in the MSSQL community. Check it out [here](
http://timradney.com/2011/06/28/getting-ahead-and-getting-involved/) From a simple ease of use approach I have heard that simple tasks in MSSQL can be quit cumbersome in Oracle. So why chose MSSQL over Oracle, in my opinion MSSQL is just better. Better product, better ease of use, and simply the best community around.
I continue : SQL Server, absolutely. I`ve worked with both and there is an enormous difference between them. Oracle is complicated, cryptical and expensive. The old trick of capturing ( IBM is expert ) the user by means of making it intentionally complicated. Once the users tame the software, at high cost, it is very unlikely to switch to other RDBMS. Oracle support is poor and very expensive. Maybe the Oracle option is justified in very big installations where an hyphotetically better performance is needed and money is not a problem, but for the great majority of middle and even big databases : SQL Server by far.
SQL server is cheaper, easier and you get a complete data platform with etl tools, bi tools, compression,partitioning, master data and master data quality tools. In oracle you have to buy these separate.