I would say that do the four if you think you can handle the workload, for example some of my friends who did 4 A Levels only ended up with about 2 free periods a week, compared to my 6, but it really depends on you.
I did an EPQ, and am now doing a history degree, and I found that it helped more than anything else with knowing how to write uni style essays and how to reference. I don't know how much essay writing is involved in an economics degree, but it might be something worth thinking about?