I have done both and Slimming world is the best for me. Ive lost over a stone so far and didnt do very well with WW. I think a lot o it is down to how supportive your group is. I found the WW snubbed me quite a lot, they all knew eah other and spoke to eah other but not any 'outsiders'. My SW group is so different, they are so friendly... but Im sure there are plenty of friendly WW groups too