Depending on time of year I'd go 10 nights minimum. It's a long flight and I don't really shrug off that UK mindset and get into the Caribbean spirit for the first couple of days. We went for 14 nights and always around the end of April so we'd have our anniversary there. Nice compromise between weather and cost I always thought.
As far as hotels are concerned we went to St James Club
I think three or four times and then to Coco Bay
the last time. We preferred Coco Bay. Less of a big hotel feel. In fact no big hotel feel at all. I'd say both of them are mid-price for Antigua.