I agree with the Breakers - simply because it's one of a kind. A real historic property. Most of it is very beautiful.
Only 2 cons I can think of. Many older rooms - although updated - are small. For the biggest best rooms - get those in the newer oceanfront addition (which isn't that new). Also - the place is *very kid friendly* - especially in the summer (when many families from central Florida come to visit for a weekend at the beach).
But so are the other "luxury" hotels in that area - and the Breakers has at least 3 pools - kid pool - regular pool and lap pool. So you stand a fighting chance of getting away from the kids. Basically - all of these luxury properties will allow a family of 3-4 to stay in a single room. So - if you visit in the summer - beware. It will not be a romantic destination for a couple trying to celebrate an anniversary.
The tennis is excellent - as is the golf (2 courses - the one at the Breakers - the Ocean Course - is the oldest in Florida - an old Donald Ross course that *is* - in part - on the ocean). L'Escalier is an excellent restaurant (by Florida standards). Stay away from the Italian restaurant unless you have kids and want pizza.
There is a new "luxury" resort in the area - Omphoy. Don't know anything about it except it's a 100% non-smoking property.
Sanibel and Captiva are great fun - especially for shelling - which is much much better in the winter than in the summer - I used to go shelling there a lot when I lived in south Florida. I would pretty much avoid the Gulf Coast in the summer (we're hot here on the Atlantic coast too - but not quite as hot).. No luxury properties there. Best bet is usually a rental condo that has been renovated within the last 10 years! My favorite time of year to visit Sanibel/Captiva is on or about the winter solstice. When the shelling is great to fantastic. The bugs are minimal. You can bike ride - go kayaking or canoeing. The Gulf will be too cold for swimming - heated pool might work. But it can get chilly there that time of year. Robyn