I've used them both and they both work pretty well. A lot of your decision will be based on what kind of maps you want to make.
Dundjinni makes excellent battlemats and small area maps. The output is very pretty and it is not real difficult to use. There are also hundreds of free bitmaps available for Dundjinni. On the con side, it is SLOW and can only cover a limited area in the map. Also it has some printing quirks but there are work arounds.
Campaign Cartographer 3 can make maps of pretty much any scale and you can zoom in and out as much as you would like. I've made a world map and then when the group is moving around in a particular area, I zoom in and print just the section of the map. The output is very attractive and it can use any of the free bitmaps that Dundjinni uses. On the con side, it takes some work to get comfortable in the software and it has its own behavior quirks.
As for buying the software without the addons, Dundjinni comes with wilderness, dungeon, and village tiles which cover a wide range, but the Castle and Temple packs have a lot of things in them that are useful. How often do you make a dungeon with an altar or giant statue? There are also modern art kits as well that are extra. I'd rate the art with vanilla Dundjinni a B
Campaign Cartographer has a wide variety of art as well. The current add on, Dungeon Designer 3, adds a lot of Dungeon mapping art and some dungeon mapping tools but they are more in the nice to have but not necessary category. I'd rate it an A.