The difference between SuaveSketch and ArtRage is about the same like between Illustrator and Photoshop: SuaveSketch is a VECTOR based drawing app whereas ArtRage is actually a PIXEL based image editor.
That said, certainly ArtRage has more value than SuaveSketch. SuaveSketch is basically a "rip off" of Apple's Sketch.app (available if you install the Developer Tools) plus the freehand tool MINUS all other useful tools you'll find in Sketch.
One can compare SuaveSketch to the Rita app (http://macupdate.com/info.php/id/19331). In that comparision Rita wins easily.