Good company, taking a cabin is highly recommended...

Good company, taking a cabin is highly recommended if taking an 18 hours trip.
The W.B. Yeats is very modern and comfortable. The Epsilon is older but still comfortable.

A note about the reclining seats: the free reclining seat on my trip to Dublin from Cherbourg with the Epsilon included a pillow and blanket for sleeping. We could sleep despite the engine's vibrations.
The 30 reclining seat on the W.B. Yeats didn't have anything, the room was cold and we barely managed to sleep... How can that be? It felt like paying 30 to sleep in a cold cinema chair.