I currently do History, Politics and Psychology which I would class as good essay subjects, which would prepare you well for any degree. However, I would only recommend History if a) you are genuinely interested in the past and b) you are willing to work hard, because I personally find it extremely challenging. It is an amazing subject though, but unless you are interested in it, I wouldn't recommend it.
Politics on the other hand is much much easier than history, both in terms of work load and in terms of the exams. I would perhaps be a better choice. AQA Politics AS has no coursework, there may be some in A2.
You do have to write essays for Psychology, but they are different to the essays you write for History and Politics, and for AQA AS I have found them to be more 'Write what you know about...' rather than developing the good essay skills of History/Politics.
So yeh, my personally choice would be Politics. The workload is manageable, the course is interesting and it should prepare you well. Having said that, history is probably better respected...but remember you are already doing some very well respected ones.
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