Terrain is different than Matrix. Terrain uses a "height map" image to create the height map(of course). A Matrix uses specific tile coordinates to doing a "height map". There are some significant differences though:
-Matrix uses tiles for the images. This is not ideal for something like a first-person shooter, but it's great for games that don't have to show a lot of detail.
-Matrix can "shift" it's height map and tiles up,down,right, and left.
-Terrain uses, as mentioned before, a "height map" image. If you are making an outside scene (zone of a game), this is ideal.
-Terrain has a fast "detail" part of the terrain you can utilize.
-Terrains are not good for an "endless" world because it takes a significant amount of time to generate the terrain. I have only looked at this aspect a little bit, so I could be wrong....
The fastest code is the code never written.