I'm in the development department at SOAS currently and have enjoyed the course in general, in terms of UCL I don't really know much about it but I would say that, in the field, SOAS is more recognised despite UCL's prestige. When looking at development departments in the UK the key places are SOAS, LSE and IDS at Sussex.
Wrt soas despite the very interesting subject matter and the uniqueness of viewpoints that you get, it can be painfully frustrating at times. With essay writing and assessment I've found there to be a general lack of support available with certain academics and tutors refusing to help students. There is no coherent marking criteria so grades are all over the place depending on the tutor and the course which makes improving your grades throughout the course of the year very difficult. Also marking is not anonymous which means that grades are very much subject to the biases of your course tutors. Also there is absolutely no support available from the department during the dissertation period, this has meant that a lot of people have got to substantial stages of their dissertation writing and found themselves very unsure of their topics and whether what they are doing is suitable or completely off topic. And lastly, while the development courses are amongst the most expensive in the UK, students are expected largely to do their dissertations from secondary research and students are not provided with support to seek out opportunities to undertake field research. If you want to do field research you have to organise it yourself which is incredibly difficult if you are someone with little experience of the field and no connections with existing development orgs.