Certainly if you ask me what is the better using Microsoft SQL server or MySQL server as a data base to store your application data, I say, of Corse, Microsoft SQL server as it offers more features. nevertheless, there are some issues to discuss when comparing the both products:
Disponibility in the market according to my region (Tunisia):
Microsoft SQL server is Less offered by the web hosting server machines as they almost use Linux and Unix platforms , moreover, even if they make use of windows server platform MySQL server is more present than Microsoft SQL server. It is rare to find a hosting server machine that offers Microsoft SQL server as a front end data base, and even if you find one, it is more expensive in cost, than the equivalent that offers MySQL server
Coherence with .Net application:
The best choice if you are .Net developer is SQL server, it demonstrates the best performance, easy to establish secure and stable connections. In addition it offers good security features. In the other hand, MySQL server offers less compatibility and more bugs in the connection stage in spite of the endeavors made to make easy the connection with .net applications. It is ore difficult to connect to MySQL data base, the best and the only way is to use ODBC the 3.51 ODBC connector and the rest, I mean OLEDB connectors, the recent ODBC connectors versions and event the others tools represent a lot of bugs and they are not stables. In the other hand, There are several ways to connect to Microsoft SQL server. The .Net environment provides special libraries to deal only with SQL server connections. More over you can use ODBC and even OLEDB for the older Microsoft SQL server versions.