I'd say that it depends on what your needs are and what you're looking to do. If you're just doing up stuff for your D&D group then it doesn't really have to be all that spectacular so I'd say CC3 is the way to go. CC3 can do some pretty nice things as there is evidence of many maps here that don't look like a CC3 map. If you want to do quick towns, CC3 is the way to go as well. If you can't draw at all then CC3 is also the best way to go.

If, however, you want to get more artsy and learn things for yourself and develop your own style then Photoshop/Gimp is the way to go. The styles are virtually limitless there and are only dependent upon how creative you are and not the people who do the artwork for Pro Fantasy.

Price is also a factor; Gimp/Inkscape are free, CC3 and its add-ons are affordable, Photoshop/Illustrator are pricey.