Edge detector offers several detection methods:
Sobel: Here, this method has no options and so is less interesting than the specific Sobel.
Prewitt: Result doesn't look different from Sobel.
Gradient: Edges are thiner, less contrasted and more blurred than Sobel.
Roberts: No evident difference from Sobel.
Differential: Edges less bright.
Laplace: Less interesting than the specific one.
Amount: a low value results in black, high-contrasted image with thin edges. A high value results in thick edges with low contrast and many colors in dark areas.
Wrap, Smear, Black: is the Wrapmode like "Displace" plug-in. It's useful for tilable image.