Terrain Material Grass Node or Foilage actors

Which is the most efficient for the renderer? I did a test with 20k with grass clumps 3 LODS by painting foliage and it ran fine.

My personal preference is to use / paint foliage because it allows me to put the grass or other foliage type where I want it with more control but I worry that I could be getting more into the scene if I use the grass node in the terrain material.

Has anyone one done a test between the two methods and have guidance?
Does either method hit the CPU or GPU harder? I am looking at the stats during run time hard to tell if one is better or not, but I am not a rendering engineer just a Level Designer.