There is less distortion using the filter then the super macro mode. Especially so if you use the +10, which is a very good lens.
Yes +10 is slightly bigger then super macro, but the lens is 10cm away from subject compared to 3cm in super macro. This makes lighting easier.
Using close up filter will fix the focal length (10cm for +10), which means with some practice u can shoot in manual focus mode quite easily. In macro, the slightest movement will make your auto focus useless.
+14 is to get a bigger magnification, in fact I'm tempted to try +20.
Hope this help.