I feel like Confusion/Psychic is definitely the best defensive moveset for Eggy. The only attackers that are strong in to him are Fire (for now at least), so Grass charge moves are pretty weak on defense. Maybe once more Dark pokemon come out it will be better, but for now it's pretty weak.
That said, it doesn't matter what the moves are so much. He's a solid defender. The grass moves will be strong against Lapras, whereas against double Psychic a Lapras can use strong ice moves without being punished.