PGSQL is great, but often when someone says MSSQL they mean the entire ecosystem. SSRS, SSIS, SSAS fall under the MSSQL umbrella and make it much more than a database. MSSQL really embraces the S of RDBMS.

MSSQL also has great tooling - another part of the ecosystem.

If I was starting today, pgsql would be my choice for licensing costs alone. But, if I already had a system built on MSSQL, it would be hard to make a business case to move (I have tried).