I played two games with Coven this morning, and I think Coven is most similar to plunder -
Coven: action, +$2, opponent -1 VP if there are curses available, completely junk opponent's deck if the game goes longer than usual (longer than double jack baseline, if only 1 person plays Coven)
Plunder: treasure, +$2, +1VP
If the game is shorter, Plunder is better, if Multi-player/long games, Coven is better.