I go to both Lavagna and La Sirene, but even though it's sort of an apples to oranges comparison, I think the food is better at La Sirene. Lavagna is trying for an Italian/pan-Mediterranean menu, while La Sirene is French. Just be aware that La Sirene is very small and in addition to BYOB, it's cash only. If the cassoulet is on the menu make sure to give it a try. It's one of the best I've had in the city.