http://examine.com says it best:
What should I eat for weight loss?
Eat less. Different diets can make this easier, so pick whichever one
best fits your lifestyle. Ultimately, you need to reduce your caloric
What's the deal with low carb diets?
Low-carb dieting is a "trick" that allows people to stop eating so much sugar and carbohydrates (flours and starches and pastas) which greatly reduces caloric intake without jeopardizing vitamin, protein or essential oils (fats) losses. Most processed carbohydrate sources are not nutrient-dense foods and are not ideal, unless you are trying to store more energy for more significant periods of exertion (e.g. marathon, distance bicycling or days of long hiking).
Carbohydrates are not what makes people fat.
Calories matter most. However, low-carb diets have been shown to improve fasting plasma glucose and insulin levels, cholesterol levels, blood triglycerides, preserve muscle mass during weight loss, and other health markers.
Low-carb dieting has side benefits for ultra-endurance athletes (increase in intramuscular triglycerides), but can negatively impact high intensity strength training by reducing muscle glycogen and forcing the body to convert protein into glucose, rather than use it for muscle building.
There is no best diet plan. There are many paths to maintaining a good diet and losing weight. The important thing to understand is that people are different in their tastes and lifestyles but not in their body metabolisms by any large degree. Resting body metabolism between extreme athletes and unfit people vary by less than 5% which means it has virtually no impact on how much you can eat or burn in daily decisions. You should be prepared to experiment and find what works for you so that you can maintain a diet that avoids an excess of calories over your lifetime however actively you choose to live.
In the end, the "best diet" is the one that you will stick to.