If you only concern is price, then Folly Field is cheaper. However, there' not much there other than condos, so you'd be doing a lot of driving.
Now, if you don't have to be oceanfront, you can find some good deals on VRBO in Shipyard. I found a condo at Brigantine Quarters that was about a 5 minute walk to the beach and a 5 minute or so bike ride (using the back private gate) to Coligny Circle. I liked the resort becasue it is small, and all the condos were renovated. It's a timeshare place, not individually owned units where one owner may have their place really nice and the nieghbor's place old and dumpy. Shipyard is a private plantation (can only get in if you are renting or own there), so the beaches are not as crowded. We had a great time, and I hope to make it back soon.