As a frequent traveller on the Oscar Wilde, I can assure you that if you suffer from claustrophobia, then the last place you need is the seating cabin. The chairs are very close together and there is not a lot of room outside of the seating area, so if the seating cabin is even half-full, it will feel very claustrophobic. Go for the cabin, spend as much time in the open area either in one of the large bars, or along the corridor, then just go to bed in the cabin when you're really tired. I think it's important to have the ensuite facilities for the additional comfort.