This could be a funny little article. "Some of the worst tools for game development ever made..."
Some people still make fantastic heightmap based terrains just with photoshop...
Many people use editors like these and find them very useful, so go
TROLL someplace else.
In answer to your question sammy, they all do far more than a simple heightmap allows, and those you have listed above provide a realtime platform to edit an outside world in wysiwyg. Some make it easy to place props like buildings and trees if thats what you want to do. They also allow you to correct errors very easily (eg, you get a gap under a house where the terrain isnt right). Some of them also provide ways of setting up properties for entities and world dynamics like weather and particles. I recommend trying the demos (and get some export samples) and see which is most suitable for what you want to do.
However, as Taumel stated with such un-deserved arrogance, a simple heightmap etc is sometimes sufficient and can produce perfectly good results if used correctly and is all thats needed. You do however get a lot more added control over your world with an editor (especially those that allow for world & prop elements like "properties" if needed). If you are interested in heightmap generators either to use as-is or in conjuction with an editor, take a look at "world machine", its v'good (tho a bit complicated at first :).