There are several pros/cons to both alternatives and a detailed tradeoff analysis is needed to draw any conclusions. In my experience the database sooner or later grinds to a halt when the tables with BLOBs become too big. After that there is no choice really. The 3GB of the OP doesn't seem too big but I'm thinking Oracle here. I have no idea when mySQL gives up, I suppose it depends on type/version of mySQL database, configuration and hardware etc.
Assuming you reach the point where you have to move the images to the file system, it pays of the design a directory structure to prevent the OS from choking and/or improve access times. You typically don't want millions of small files in one directory.
As I mentioned an alternative is a dedicated database product to store the images. These databases are optimized for that purpose.