The ruffle foot will gather and is adjusted by the stitch length, it can also make gathers and sew to another piece of fabric at the same time. The Gathering attachment makes pleats, tiny or big, adjustable too. It can pleat every stitch, or every 6th one, or even 12 stitches apart. The depth is also adjustable. And can be sewn to another fabric too. The two are entirely different, so depending on how you plan to use them is the one you will purchase. I use the attachment much more often myself. Betty_________________