I've heard that people fill the plastic eggs with sand to give them a more realistic weight and make it harder to push them out of the nesting boxes. Mine are empty, but they've never been pushed out or opened. Perhaps I have very gentle chickens!
I think using what's easiest is best. We have young kids, so we have a bag full of plastic eggs in the garage. No one here plays golf or ping pong.

I think using what's easiest is best. We have young kids, so we have a bag full of plastic eggs in the garage. No one here plays golf or ping pong.