Hello!
As the material specifies, the landscape material is designed for large landscapes, and is better optimized for them. Vetex paint on the other hand is designed for props or objects that are not going to be always rendered. Another difference is that you can create an Automatic landscape material depending on the height of the terrain.
Yet if you want to make a more controled or a a terrain that is not a landscape, I recommend using vertex paint as shown in the following video
Hope this helps!