(1) Dieting by calorie restriction alone works, but it's tough. You're hungry a lot of the time, and you need to maintain a fairly high level of exercise to keep your metabolic rate up.
(2) The Atkins diet, in practice, works better. The high levels of protein and fat keep you satiated. And, having tracked calories while on Atkins, in my experience it tends to be a calorie reduction diet as well. You just don't want to eat that much meat. It's not so hard to maintain an exercise regime, although I find retaining muscle mass isn't easy; weight training gets a lot tougher. And it's very effective. 5 - 10 pounds in the first week is typical, and it's not all water. You can get enough zero carb roughage with an intelligently constructed salad every couple of days.
I believe Atkins weight loss is due to two effects, both significant, but whose exact contributions I haven't tried to measure. One is the raw calorie reduction. The second is ketosis, which is how Atkins himself thought it worked. Basically, after a couple of days of extreme low carbohydrate intake, your body runs out of its glucose stores, and it has to make glucose by a process called gluconeogenesis. It can do that by using a small portion of a fat molecule, or from some amino acids, but both processes are inefficient, and the result is a lot of the rest of the fat gets converted to acetoacetic acid and eventually acetone, a ketone. Your body can use the 'ketone bodies' but you're producing a lot of them, so some of them get excreted, and with that you lose the calories you would have gotten from metabolizing them properly. So there's some extra weight reduction, but you don't excrete enough to account for all the weight reduction.
In practice, I find that a bit of attention to the calories, combined with Atkins, is still easy to maintain, and more effective than raw, eat-all-the-fat-and-protein-you-want Atkins.
(3) I think a low, but not zero carbohydrate diet is a good long term maintenance diet, particularly when you get older. Eating lots of carbs these days just gives me glucose swings, and my doctor assures me I'm not pre diabetic. And the carbs should come mostly in vegetables. South Beach, maybe, not Atkins.