The tool to use depends maily on how you want to implement your terrain.
Is it just for 2D Backroundshots,
or for making a terrainmodel?

If then, do you want to use a multitexture terrain, or
a terrain with a maintexture that has shadows and coloration baked on it?

I made some nice things with Terragen,
it can be used for skycubes, and making 3d terrain with shadows too.

In the end, the tool + workflow must end in a .hmp file with the correct skins.
So making a nice terrain in a tools does not mean you have it in this quality in the game.