If you are talking about a studio stay, I might rule out OKW because their studios have 2 queens and no couch, the rest of it depends on the activities they'd like to participate in. All of the DVC's all have reasons why they can all work very, very well for a romantic trip, and with the extra Disney magic in the air...
SSR has several completely remote view rooms (like golf-course only or DTD view) where you do not see any other resort room from your balcony, but also has buildings that face other buildings (across a pond) i.e Springs. You can order food to your room at SSR, but it would be from outside delivery like Giordano's (pizza/pasta), more limitied selection and not as fancy in presentation, but much better if you are a pizza lover)
I got the feeling that at AKV you could usually see other rooms from your balcony. I do think the public areas and restaurant choices may seem more romanitic. AKV does not have a quiet pool, but by that time the new Kidani pool should be open and the Jambo pool may have few kids, and with the landscaping there are many lush areas that seem somewhat quiet..
In the end you need to figure what activities they want on their ideal trip (Spa, DTD, Park proximity, In-hotel services...) and choose the resort that c