Speed/size advantage to SQL?

[MK27]

explains why flat files should not be used(or should be used in some contexts alone).

Thanks for that Steve, but that is not exactly what I'm asking, since both an SQL database and a text-file *could* be implemented in a "flat-file" way.

By "set of directories and text-files" I meant something that would be accessed in a "relational" way by the app, not just one mega file that I would parse line by line and turn into a data structure.

So I guess this would come down to the details. I was just trying to fish around and see if there is not some "beyond the obvious" aspect to SQL. There does not have to be; I can understand it's popularity purely on the basis of its ease-of-use, conformance to a certain standard, and universality. In fact, I probably will stick to it because of that...