So AC, you really *think* you know what you are talking about, but in fact you really don't.
Postgres - in a high transaction environment if the vacuum goes sideways you just simply crash and burn and your data gets scrambled. On top of that, I double dare you to try and move from one machine to another, much less one hard drive to another.
MySQL - ACID much?
SQLLite Uhmm for little tiny projects, sure as long as you don't need ACID or more then one person using it.
Oracle - IF and it is a BIG ONE - you actually know how to use it, (If you have had the proper training, or you have been using it forever ) It will spin circles around pretty much anything out there. Do stupid things with it and just like any of the rest of them that are enterprise class ( MS-SQL, DB2, Postgres, Informix etc. ) they will not perform up to anyone's expectations.
So please go have a big frosty glass of Shut The Fuck Up.