Php Data Grid

what would the performance difference be between storing data in files vs SQL?
I have a Flash app that links to php on the server side. The flash add displays a section of a 2d grid, each grid square is a file.
the advantage to having it as files is it doesn’t need to run any script to display the data, only to change it, I like this, but would it be quicker if it was in SQL? and how much?
basically each grid square is 256×256 pixel, and the flash script displays 4 at once, and as you move around it needs to load the new squares, and multiple people can view the grid, so there are many reads.
If you are always retrieving or updating data sequentially, flat files are just as fast if not faster than databases. If you do so randomly but can index for direct access, same thing. Where databases blow flat files out of the water is when you 1) have complex criteria for determining what to retrieve or update, 2) want to combine information from multiple files (tables) and/or 3) perform analysis or group information from the various files/tables.
PEAR Video Tutorial 5 Building a Datagrid from an SQL result set