Atkins is an atrocious diet. Sure, you'll lose weight, but you're starving you body for carbs and ODing on fat and cholesterol. Somebody please explain to me how THAT is supposed to be good for you!
Weight Watchers is a great diet, but people seem to get this weird idea that they can be on some "special" diet for a while, lose a bunch of weight fast, then go back to their old habits, which is totally absurd and self-defeating.
If your tendency is to gain weight there's only one way to get the extra pounds off and keep them off: Eat right, eat less, work out more, and keep doing it for the rest of your life.
The simple answer is eat like a caveman: lots of the stuff that's easy to catch (fruit, vegetables, grain), moderate amounts of the stuff that's harder to catch (fish), and very little of the stuff that fights back (cows and pigs and such had much different personalities back in those days).
On my doctor's recommendation I totally cut out most dairy (no milk, half-and-half, sour cream, or ice-cream), less beef , chicken and pork, and more fish, fruit vegetables, and grains. Threw in a little cycling and a little walking. It took three years, but I lost 25 pounds and went back to my weight of 18 years old, and my cholesterol went from 300 down to 200.
It's the only way.