I have done both diets (and many others I might add!!) and I find they both offer me different things.
As already said, its whatever suits....there is no right or wrong, they all work if you stick with them and you are more like to stick at a diet if it fits in with your lifestyle.
I have recently swapped back to WW from SW because I want to excercise some portion control and eat more veg. Now, I know I can do that on SW but the simple answer is, I don't!!! I fill up on other foods and therefore don't eat enough veg. On WW, however, in order to keep within my points, I find I have to bulk out my meals (with veg) in order to keep my massive appetite at bay!! lol I must add at this point, I do love veg, so I'm not eating something I don't like for the sake of the diet!!
As for eating 'rubbish' foods such as white bread and chocolate cereal on WW, I find my points don't allow it as it wouldn't leave me with enough points for 'real' food but if others can get away with it, why not, afterall, you are allowed on SW too, thats what syns are for!!!
Naturally we are all here for the same reason ultimately and just because we have lost weight and are on diets doesn't suddenly make us all saints and not want to 'have a bit of what you fancy' occasionally.
Personally, I have nearly always eaten fairly healthily even when not following a plan but I obviously eat too much of it, so for me at the moment, WW is the way to go....