The decision on SQL Server versus Oracle comes down to the size of your implementation. Oracle can handle data warehouses up into the 1-2TB range before you have to really start getting advanced in your performance tuning tactics. SQL Server's ceiling is well below that level.
Oracle will run fine on the Wintel platform as well as any of the mainstream Unix platforms. SQL Server is is much more tied into the Wintel platform.
This was first published in March 2005