I did LL in 2005 for 2 weeks before falling pregnant with my DS2, i'm now doing Cambridge.
One of the big pro's for LL is the counselling element, if you feel you have major issues with food you need to address then LL is probably the best option. Saying that, it is twice as expensive - £66 per week (i think?) compared to Cambridge (£32.55 approx).
Cambridge diet works on the same principle, but while you may be lucky and get a fantastic counsellor who is prepared to spend time with you talking about your problems, issues etc, you may equally get a naff one who pretty much just gives your stuff and turfs you out. I'm lucky, my counsellor is fab, she spends half an hour with me one on one chatting about the diet, how i'm feeling, what sort of week i've had etc, she's really good. What I don't get is the Cognitive Behavioural Therapy you get with LL. I can't afford LL which is why i'm doing Cambridge.
You do get more choice flavourwise with Cambridge which can be seen as a good or bad thing.
Either way, there are lots of us about doing both diets so always someone to give you some moral support.
Good luck with whatever you choose, you won't regret doing it! I'm 5 weeks in a 30lbs lighter, my life has changed, i've got more energy, more self confidence, i'm generally a much happier person!
Gemma x