Hi! I decided to go with LSE's Social Policy & Development: NGOs option. The UCL course was a little too focused on the planning aspect for me (I realised that I would rather focus on social policy) and, since I haven't worked professionally (only as a volunteer) in the NGO sector before, I figured that a more well-rounded degree might suit my needs better than the more specific Kings programme. The LSE course won out for me because of the breadth of the offered courses and the university's reputation in the social policy field, which I would argue is slightly stronger than UCL's - especially outside of the UK.
I'm only 3 weeks into my programme so far but I am really enjoying it and finding it very interesting. The choice of courses is great, in that you can focus on pretty much any area of social policy in the developing world that you want to, and there is also a bit of leniency regarding taking a few courses outside of the department as long as you are justified in doing so. For instance, I've taken a course from the Gender Institute because my interests lie in gender in development. The professors are also great - really accessible to Masters students - and you get lots of time with them in fairly small seminars. There are about 60 students taking the Social Policy & Development course and they represent a huge range of countries, which is great since so many people have experience in the development sector already.
I would definitely recommend this course so far, but I'd suggest you have a look at the course offerings to see if they match your interests. If planning is your thing, I'd go with UCL, but if you're more interested in social policy, I'd go with LSE. Either way I don't think you can really go wrong! Good luck!