If your goal is maximum events per week, you’re better off using
event + counterpart rather than event + ditto. Even if both have
about the same event probability per egg, the higher egg production
rate from “get along very well” will give you more total events
over time. The only reason to use Ditto would be if you don’t have
a compatible counterpart or you’re trying to pass down something
that only Ditto can help with.