Few people knows about this series, but is my favourite one, and is my divine job to make people known the awesome series.
Plots are mystery murder in both series, In first cas Higurashi is mixed with friendships topics and fight against fate. In Umineko's case it goes more extreme and mix mystery with fantasy creating an unique story about the battle between reality and fantasy
If anyone is interested to known more about these series, just tell me, as I say is a divine mission xD