I don't consider myself brand loyal about technology, I am pretty open to most things, but I really do not like Microsoft products given my first hand experiences.
But I love SQL Server .. I attribute that to the fact that it was originally written by Sybase.
And it is free, at least SQL Server Express is.
My experience with database performance, SQL Server has an excellent query optimizer that allows me to pretty much just index all my foreign keys and get really optimal performance.
But the love/hate relationship continues. I spent an inordinate amount of time trying to figure out what license I needed to run a SQL Server 2012 with a SQL Server Express (free) license. Eventually I figured out what was considered acceptable, but still seemed to be in conflict with the TOS.
I have migrated my larger databases in to MySQL without any issues other than the terrible sub-query performance. Apparently MariaDB has addressed this, but still pretty far down the list to try.