they will both work just as well as each other if you follow the programme. slimming world isharder in my opinion as you hve to stick to either mainly veggie or mainly meat eating days.
you have to be prepared to stay on these plans for the rest of your life, that is why they dont always work and thats why they make so much money from people who have gone back to their old ways. you are much better off by adjusting your diet, cutting back (not out) all the crap and finding something to replace the bad things, thus making your own diet. start walking at a pace increasing time and momentum over a period of time. the paul mckenna book helps. it really does