Others have covered some of the enterprisey and ecosystem reasons around SQL Server. I'll add a few thoughts, but try not to reiterate too much. Note that I am

Others have covered some of the enterprisey and ecosystem reasons around SQL Server. I'll add a few thoughts, but try not to reiterate too much. Note that I am speaking about Enterprise Edition which is ~$14K/2cores (sold in 2 core units) (other editions offer subsets of these features). This is all off the top of my head. Ecosystem As mentioned, you get core SQL Server, along with a number of integrated tools that range from adequate to best in class: * SSIS for ETL * SSRS for reporting - includes traditional paginated reports, Power View for visual analysis and exploration (in 2016 gets native mobile apps and major overhaul) * SSAS - Multidimensional for traditional OLAP, data mining; Tabular for in-memory columnstore * CLR - everything has access to CLR languages for customizability and scripting * Azure - easy transition from on-prem to cloud either with IaaS and pre-configured DB VMs or Azure SQL and Azure DW for SaaS with syntax and feature compatibility; very strong hybrid infrastructure story Features All of these are native * In-memory OLTP - memory optimized tables, optionally transactionally persisted to disk or not, with sprocs compiled to native code * Columnstore index - optionally memory-optimized tables with clustered columnstore for hybrid OLTP / OLAP workload * HA groups for native replication and failover story * Native R integration (coming SQL Server 2016) * Integrated row-level security * Encryption for data at rest and in transit (more of an Azure SQL piece) * Native master data and data quality services I don't know if you care much (but CIOs and IT directors of large organizations do), but SQL Server 2014 is the absolute leader in Gartner's magic quadrant for mission-critical application development, and Microsoft is in a leadership position for BI as well. Believe it or not, TCO is one of the largest talking points for Microsoft data platform account executives and solution sellers. Especially when placed against Oracle that story is strong. We have customers (we being the company I work for - BI and analytics consultancy) coming to SQL Server from every platform you can imagine. There are also many customers leaving SQL Server for every other platform. At this point in time Microsoft is doing a pretty good job of making sure that first number is larger than the second by a healthy margin.