http://stackoverflow.com/questions/3743632/gis-postgis-postgresql-vs-mysql-vs-sql-server

What database is best for the underlying data store for all this data? Here’s my desires:

• I’m familiar with the DBMS. I’m weakest with Postgresql,but I am
  willing to learn if everything else checks out.
  It does well with GIS
  queries. Google searches suggest that Postgresql + PostGIS may be the
  strongest? At least a lot of products seem to use it. MysqL’s Spatial
  Extensions seem comparatively minimal? Low cost. Despite the 10GB DB
  limit in sql Server Express 2008 R2,I’m not sure I want to live with
  this and other limitations of the free version. Not antagonistic with
  Microsoft .NET Framework. Thanks to Connector/Net 6.3.4,MysqL works
  well C# and .NET Framework 4 programs. It fully supports .NET 4’s
  Entity Framework. I cannot find any noncommercial Postgresql
  equivalent,although I’m not opposed to paying $180 for Devart’s
  dotConnect for Postgresql Professional Edition. Compatible with R. It
  appears all 3 of these can talk with R using ODBC,so may not be an
  issue.

I’ve already done some development using MysqL,but I can change if necessary

If you are interested in a thorough comparison,I recommend “Cross Compare sql Server 2008 Spatial,Postgresql/PostGIS 1.3-1.4,MysqL 5-6” and/or “Compare sql Server 2008 R2,Oracle 11G R2,Postgresql/PostGIS 1.5 Spatial Features” by Boston GIS.

Considering your points:

I’m familiar with the DBMS: setting up a PostGIS database on Windows is easy,using PgAdmin3 management is straight-forward too It does well with GIS queries: PostGIS is definitely strongest of the three,only Oracle Spatial would be comparable but is disqualified if you consider it’s costs Low cost: +1 for PostGIS for sure Not antagonistic with Microsoft .NET Framework: You should at least be able to connect via ODBC (see Postgres wiki) Compatible with R: shouldn’t be a problem with any of the three