I don't know which one you're talking about, but I have both, what they call an edge-joining foot and the foot with the quarter-inch guide on the side. Both work well. The edge-joining foot is the one I use for "real" SITD quilting, because the little edge in the middle just stays in the seam as it goes along. The one with the 1/4 inch guide is good for piecing and also for quilting a 1/4 inch from the seams.
One word of warning. Be sure and get the edge-joining foot that's made "JUST" for your machine. The one I have was supposed to work on both the machine I bought it for and the new I got several years later. It didn't and I almost wrecked my sewing machine when I tried to use it.