What should bd my 3rd Alevel?Watch
I would say, based on what other people in the classes said, those who did biology found that it made biopsychology easier.
In terms of the case studies, the same case studies can be used in many topics so it's easy to reduce the amount to learn and the specification case studies will be repeated so many times that you'll find that it's easy to recall them. Although there's alot of evaluation points to remember, like the case studies, many overlap with multiple topics so this can be used to help reduce the content
In terms of sociology, it's just as content heavy but like psychology you can reduce content and decide which sociologists you want to remember.
For essays, I would say psychology essays have a more specific structure so essay writing skills are more likely to be needed/useful for sociology- sociology also has fewer short answer questions
Hope this helps a bit and I'm happy to answer any questions about either subject