Slimming world say if you stick to the plan 100% you should lose on average 7lbs a month, you can lose up to a stone in a month and previously when I have done this plan I have lost 4st 7lbs in 5 months and got to target, but that was by sticking to it 100% for all that time which is hard to do and maintain a social life!
I think with CD your weight loss eventually slows to 2-3lbs a week and this is easily achieveable with SW, but the bonus is you can eat!, also with CD if you have a bad day you can pile weight on, that doesn't happen with SW and you can usually find if you have a bad day but get straight back on it you will still lose.
I have tried CD and yes whilst I like the rapid weight loss you get, I just feel for me it is unsustainable and I just feel thoroughly miserable and like I am missing out, at least with SW you can incorporate it into your daily life with minimum fuss or effort