I started SW 3 weeks ago, and I'm doing EE. I don't know anything about the other plans.
I was sceptical too about EE, wondering how unlimited free foods would help me to lose weight. But I followed the plan to the letter and my first week I lost 4lbs and my second 3.5lbs and got my half stone award. I was astonished, I've never been one to lose more than 2lbs a week, usually I lose 1lb a week. So to lose an average of 4lbs so far is crazy, and I feel like I've eaten too much food for a 'diet'.
But SW isn't a diet, it's a healthy way of eating. And as others have said, because foods are free and unlimited it means that you can eat them when you are truly hungry and stop when you are comfortably full. If you comfort eat when you feel depressed for example, and not physically hungry, and keep eating until you are stuffed rather than comfortably full then you will encounter problems and weight gain.
But yes if you get hungry at midnight then you can eat! If you get hungry in between meals you can eat! SW heavily suggest that you snack on superfree foods first ie fruits and vegetables rather than choosing synned foods straight away.
Good luck, give the plan a go, and if you follow it to the letter then I fully expect you'll lose weight. You might get bloated/constipated initially that might mean you don't lose weight in the first week or so, but don't worry if that happens, your body will adjust.