History is a lot of work and quite-time consuming, admittedly, but it's one of the most interesting subjects IMO. I do Tsarist and Communist Russia and it's a pretty decent course, not as good as the other one I'm taking, but still very good.
Sociology is definitely easier, though that hasn't been the case for me for some reason - got an A in the mock for History and a B in Sociology.
Also, if you take History, Politics and Geography at A2 you'll have two facilitating subjects rather than one if you pick Sociology (assuming you wouldn't drop Geography)