Postgres vs SQL Server
Bent Ozar has a good article about why benchmarking is rarely seen based on Dr. David DeWitt. 


  BENCHMARK TESTING. You must obtain Microsoft’s prior written approval
  to disclose to a third party the results of any benchmark test of the
  software.


But, one is free and one isn't so there is a big difference to consider among the laundry list of others (IDE, HA/DR, Auditing, Server operating systems, Supported laguages, etc). 

There are also some older posts on Stackoverflow comparing the two, with many folks providing their opinions.


GIS: PostGIS/PostgreSQL vs. MySql vs. SQL Server? 
DB2 vs PostgreSQL vs SQL Server
Brent Ozar: Two Important Differences Between SQL Server &amp; PostgreSQL


Dr. Dewitt also has a great video about query optimization. which is slightly relevant but more so just a great watch.