For the whole cluster LOD 1 has 120 Tris (720 Tris at LOD 0) and the single grassbush has 108 Tris (18 Tris at LOD 1).
We’ll stay with foilage, since was one of the main reasons for the engine switch to UE4 (beside a few other reasons).
I really hope the is a way to get grass working properly in UE4