Agreed ... Ghost shrimp have a very difficult diet to duplicate in an aquarium setting. Often newborns end up starving ... though in a well established tank there may be enough for them to munch on, I wouldn't bank on it though. In addition, any newborns will basically become food for any fish in the tank.
RCS on the other hand will munch on whatever the adults do and they breed so often you're bound to double your population in a few weeks to months. I started with 14 at the beginning of Oct and as of today I found I have 10-12 newborns upping my number to about 30. Starting with 10 RCS should give you a good male to female ratio to start a colony.