The key here is to figure out which one is most suitable for your lifestyle and fitness goals. I chose the Zone eating plan (I call it a plan, not a diet, since I was looking to gain weight in the beginning) because its 40-30-30 ratio of protein, carbs and fat made the most sense to me.
A long time ago all I did was limit my calories. It helped control my weight but I was far from healthy and toned because although I was eating a good number of calories, those calories were empty as they came from the wrong kinds of foods -- starchy, low-fat, high-carb food.
I had a difficult time understanding the Zone at first so I kept a food log for about two weeks just to see how much was one "block" of a certain food and how it looked on my plate. It was important that I knew how it looked on my plate because I was then able to eyeball my portions, instead of measuring them all the time. I know it works for me because my stubborn, chubby areas get even softer and mushier when I am off the Zone.
The thing I like most about this eating plan is that there are no foods that are strictly off-limits. There are only "favorable" and "unfavorable" foods. The unfavorables you can still have but in moderation. I do not, however, follow the calculations in the book as far as protein requirements go. Since I'm trying to gain muscle, I take in more protein (in the forms of lean chicken, egg whites, tofu, salmon and tuna) than the book requires.
When I first tried the Zone, I followed it to the T -- according to its calculations based on my measurements. Man! Because I am working out 5-6 days a week, I was hungry all the time. So I had to increase my portions to keep my body from starving. So far it's working, albeit very slowly. But I'll take what I can get.
In a nutshell, the Zone has taught me to eat the RIGHT AMOUNTS of the RIGHT KINDS of foods, as close to its original state as possible (i.e., unprocessed).
If you skip all the scientific and technical jargon of the book, you'll read things you've heard before: Drink lots of water. Eat your fruits and vegetables. Choose lean cuts of meat. Avoid bad fats. Use small amounts of good fats in your cooking. Spread out your meals into five small ones in one day. Never let yourself get hungry as this will lead you to eat more than you need in your next meal. It's really all pretty simple once you've got the hang of it. The hard part is staying away from temptation.
Which leads me to my next point -- once you've chosen an eating plan that's right for you, stick to it. Hope this helps.
Pinky