Hi,
The actual difference is the subjects that you choose to major in. For ba in arts you have to choose from the subjects like language , history, geography , polity , psychology,  sociology. And for ba in social science you choose from subjects like , history , geography , polity ,etc. You have two choose 2 major subjects in each course . Although there is not much of a difference but they are two different degrees.
In ba social science students can choose subjects of only humanity while in ba arts they can choose humanity plus literature subject.
Hope it helps...

Hello,

Generally BA hons arts is a stream where we particular study subjects of humanities like Philosophy, English, Geography, History, Political science etc, in BA hons a particular subject is taught to a deeper extent, but if you're asking particularly about BHU BA hons arts and BA hons Social science then for BA hons arts and BA hons Social science there are two different facilities, subjects like Psychology, sociology, history are taught by social science faculty while subjects like Hindi, English, French are taught by BA hons arts faculty.


Hope this helps, all the best.