What's better/faster? MySql or FileSystem?
The file system is useful if you are looking for a particular file, as operating systems maintain a sort of index. However, the contents of a txt file won't be indexed, which is one of the main advantages of a database. Another is understanding the relational model, so that data doesn't need to be repeated over and over. Another is understanding types. If you have a txt file, you'll need to parse numbers, dates, etc.

So - the file system might work for you in some cases, but certainly not all.