I can only speak about ksTree. It seems to have an "auto-normals function". Meaning that if you have the origin set somehwere on the trunk axis, it will autmatically orient normals in a sphere-like manner in order to achieve the best lightning; hence making the trees NOT look like cardboards.
For the ksGrass.. not really sure. Maybe just the posibility to use multiple "layers" ? (like adding some variation).