Both The Atkins Diet and the SouthBeach Diet, work by lowering your daily carb intake. The Atkins diet encourages one to cut out all carbs; good, bad or indifferent. [see Simple Carbohydrates.andComplex Carbohydrates.]
They are also allowed to eat unlimited amounts of protein and saturated fat.
The main distinction between these two diets is that the SouthBeach Diet does not require elimination of carbs, but only a change in the type of carbs consumed. Also, the SouthBeach Diet does not allow consumption of saturated fat, which is commonly linked with cardiovascular disease. Instead, it promotes the consumption of unsaturated fats, which are proven to promote better health.

South Beach Vs. Atkins

Atkins

dieters following this diet tend to see a dramatic weight loss over the first week or two. The diet works by reducing the consumption of carbohydrates to a minimum, and dieters are advised to eat foods that are high in protein, many of which are also high in fat. Although weight loss can be very rapid, about 10-15 pounds in a 2 week period. This diet has been the focus of a great deal of controversy over the years due to its restrictive nature. After the initial weight loss, carbs are meant to be slowly re-introduced in order to maintain the weight loss. The advantages are rapid weight loss, good quick-fix diet and it is proven to work. The disadvantagesare very restrictive, can get dull and is not suitable for vegetarians.

South Beach diet

With the South Beach diet you will mainly eat meat, chicken, turkey, fish, and shellfish. The diet will also include vegetables, eggs, cheese, and nuts. Although for the first 14 days you won't be able to eat any potatoes, rice, bread, baked goods or fruit. In addition, no candy, sugar and alcoholic beverages. These things will slowly get reintorduced to your diet.