It depends on the Buyer. However, a Sunporch can be used in rain or shine, keeps the bugs out, and if it possilbe, has the ability to close the windows for year-round enjoyment! Neither a deck nor a sunporch technically add value to a home, but it does make the home more desirable to buyers making them willing to pay a little more than other comparable homes. A deck has to be maintained more often and is only practical when it is warm outside (not in the cold weather or the Hot summer). My vote would be the sunporch for it's versibility. Also, since you are in South Hampton the typical buyer for that area would prefer a sunporch over a deck.