Hi there!
Last year, I applied to LSE, SOAS, IDS, Manchester, Bristol and UEA for Postgrad degree in Development Studies. Even before receiving the offers, I have already decided to study in IDS. Eventually, I received a 9,000 pound scholarship from Bristol but still I believe I should go for IDS. I was accepted to all but LSE (which I am happy that I didn't get an offer from LSE because that made my life easier!). And I decided to study MA Poverty and Development at IDS.
I do accept the fact that LSE might have better international reputation and could offer exciting internship/employment opportunities as it is in London but even if I got offer from LSE, I would still have chosen IDS. The reasons are that the course that I am studying perfectly fits me and my expectations are, indeed, met. IDS is a research institute that teaches and there is always something going on! Secondly, Brighton is an amazing city and the campus is awesome! It is indeed, cheaper than London with the accommodation fees ranging around 400-500 pound and other costs could range from 100-400 depending on your spending style. I cannot make comparisons with London but I believe it is cheaper. Thirdly, I am from Myanmar and there are not much professors researching on the country. Only in IDS, I found one really inspiring professor who has done researches in Myanmar. However, I do get jealous of the students at LSE who are exposed to amazing guest speakers!! After all, the programmes take only one year and time flies so fast! What you could gain from the programme is friendship, reflections and attitude. You need to be in the place where you think you can absorb as much as possible and enjoy the journey! So, as Megan has said, all three are reputable and you should make the decision based on your taste, interest and expectation!
As a side note, if you are planning to get into really top organisations (UN, some big consultancies), they do have preferences from where they graduate. For instance, there is a consultant who always hires 2-3 graduates from IDS every year but at the same time, some UN agencies prefer LSE graduates. So, if you already have in mind which organisation that you want to go for, you might want to research where most of the employees come from.
I hope you found this useful and feel free to message or contact me if you have any questions!