Have never eaten at Kouzinna - but we ate at Captain's Grill in March on our HM and I was very underwhelmed. I have read great things about Kouzinna though!
Captains grill is what I would choose. We went to Kouzzina in Aug and were not that thrilled. DH is greek and we eat at a lot of local greek restaurants that are much better. The food at YC at any of the restaurants is really good.