Atkins vs South Beach Diet

Among low carb diets, the South Beach and Atkins diets are quite popular. Many wonder about the similarities and differences, and indeed there are both striking similarities and dramatic differences in how Agatston and Atkins designed their weight loss diets.
Similarities

Structure:
The structure of the two diets is almost identical. They both start with a restrictive phase lasting about two weeks. Analysis of the South Beach Phase One menus have showed them to have about the same amount of carbohydrate as Atkins Induction (although it could be higher depending upon individual choices). In the second phase, they both slowly add carbohydrate to find the optimal level for each person. When the desired weight is reached, they go to a maintenance phase.
Emphasis on finding individual carb level: I’m a big believer that different people have different sensitivities to carbs, and one thing I really like about both of these plans is that they are structured to help someone find the level of carbohydrate that works for him.

“Good vs bad” carbs:
Although Agatston advertises this more than Atkins, both Atkins and South Beach differentiate between various carbohydrate sources. They both advise against eating refined carbs (sugars, white flour, etc.). For other sources of carbohydrate, Atkins has a “carb ladder” of when to what to add what foods to the diet, based mostly on glycemic load. The South Beach Diet mostly uses the glycemic index to differentiate between “good” and “bad” carbohydrate sources.

Differences

Fats:
The most obvious difference between the two plans is the advice concerning fat in the diet.
South Beach advises minimizing saturated fat such as not eating butter or the dark meat of poultry. The oils Agatston recommends (olive and canola) have a lot of monounsaturated fat. He also emphasizes getting adequate Omega-3 fatty acids. Agatston doesn’t mention Omega-6 fatty acids, and is vague on polyunsaturated fats as a class, but seems to say they are good.
Atkins (using the most recent book), advises eating a variety of fats. Omega 3s and 6s are recommended to be balanced, which means that many oils that are primarily Omega-6, such as corn oil, should be avoided. Saturated fats such as butter are (famously) allowed in greater amounts than South Beach, but Omega-3s and monounsaturates are emphasized.
Both hate trans fats (as well they should).

Counting carb grams vs. carb portions:
The way carbohydrate is accounted for is different in the two diets.
Atkins requires counting all carbohydrate that is digestible; mostly this means carbohydrate that isn’t fiber. Daily carb intake is accounted for by counting every gram eaten.
South Beach does not limit non-starchy vegetables. Other sources of carbohydrate are accounted for by the size and number of portions. Most people would probably find this is simpler than gram counting.