There will undoubtably be a number of good responses here to your question, but I'd like to share my opinion. For me, the answer comes down to tooling. I make frequent use of Integration Services, Reporting Services, the Server Agent, Profiler, and other services I'm not remembering at the moment. In my mind, SQL Server represents an ecosystem of tools and services that are simply part of the package (no additional cost) and are fully supported and integrated as part of a comprehensive suite.