I like both history and political science. With respect to the future prospects, which one is better?

It depends on you as which would be better for you because none of them is good or bad. Both of them have different concepts.

Both, in terms of scope, are better as now many students are going towards a choice of BA (Hons) history and political science as they see political science as a debate forum subject and with history, they go for sociology, so both are good.