New homes are oftern more expensive on a square foot basis then existing resale homes. This is not specific to any one geographic area.
As to which is a better deal? That is a tough question and the answer will be very subjective. Everyone has different reasons for purchasing a home and choosing a specific location. The best deal is the home that best suits your needs and is within your budget.
My best advice is to find an agent in the South Brunswick area that specializes in that area. They can give you the best advice on what is available in that market place - and which may be the best deal for you - based upon your needs.