I read forums on all three diets because I'm interested in the places where they cross over.
Dukan: the pros for me would be being able to eat yogurt, although youre not supposed to have flavoured ones any more so that has mostly lost its appeal. And being able to have extra tomato and butternut squash.
Dukan cons: taking the skin off your chicken and cooking with no butter or oil feels too austere for me - fry light sends me back to my weight watcher days. All the emphasis on low fat unsettles me - I don't believe most low fat products are good for you, and low fat natural foods are low on flavour. I just don't think I'd enjoy the food or feel as happy on Dukan, and apart from veggies there doesn't seem to be as wide a variety of things to eat. As I say it just feels too diety. Atkins is also far easier to eat out on, and as hard as it can be to find emergency snacks on Atkins, it's harder on Dukan. I think most of them are only in mild ketosis if they're in ketosis at all, so I'd also likely be hungrier. Dukan works just as well as Atkins if you can stick to it but I doubt I could.
Paleo in my opinion is the perfect maintenance diet after you lose the weight on low carb / Atkins - but it's not as effective for weight loss itself unless you follow paleo AND cut the carbs right down - which is basically Atkins with a few more rules.