I have only eaten at Castle Dargan, on two occasions, and found the service to be very slapdash. Both times was carvery, no cuttlery both times and slow coming when we pointed it out, and on one of the occasions, while we went up to get deserts, our unfinished drinks were cleared from the table. Haven't been to Cromleach, but close friends have been to stay for a weekend recently, and were very impressed with the place. She's a real foodie, and said the food in the restaurant was really good. Anyway, Sligo is beautiful, so I'm sure you will have a good time.