i would not do 4 unless the fourth is further maths or a language that you speak at home, unless your applying for a very competitive course at a top university, eg law, engineering, medicine, comp sci, econ etc, its not worth all the extra pressure, especially in year 2/year 13. most universities only look for 3 a levels anyways.
as i saw what other people said in the thread, taking a mix of both is the best option, i would take 4 to start and then drop your least favourite about a month in. definitely take maths and english though, they are very versatile subjects which are sought after by all universities.