MSSQL's text comparison by default is case insensitive. Its limit clause is nonstandard (select top 10 * from . . .). Its syntax for other things, like trimming or casting, is just much more typing. Installing the driver on a Linux server is several times harder than Postgres. When I get the syntax wrong, all it gives me "General Error." The command-line tool to Postgres, psql, works much more smoothly and has many more features than MSSQL's tsql (and Oracle's isql, for that matter).

If you use MSSQL all the time, I have no doubt that you get along fine. You can get used to its ways, and most applications don't need features that aren't shared by almost all databases.

I didn't mean that if you use MSSQL then the app will always noticeably work worse than if you based it on Postgres. It's just that for someone who switches back and forth, MSSQL makes my life less enjoyable, provides no benefit, and costs a lot more money.