I hope that in future versions of Corona will be supported Hair render, in a similar way as in Vray, or Corona team maybe make Corona own scatter for C4D. Anyway it is necessary to be patient, I have no doubt that we will be rewarded with some nice solution.
Do not know how works surface Spread, but mograf have some..... limitations. For example, when distribute clones on surface you need much more clones than is required or be visible, but they eat your resources. So you can with Hair make distribution for clones. In Hair menu choose add Hair guides and set guides numbers to 1 and for min. spacing put value depending of grass patch size, then simply draw. In generate tab chose spline, make Hair object editable, disable hair render. In cloner menu chose object mode, and put hair spline there. In that way have control how many clones have and his distribution.
I hope you understand my Tarzan tongue :p
