Before going to University, everyone convinced me to choose traditional, respected subjects like Physics and Maths because that's what good universities want to see. This was a huge mistake.
I struggled massively with Physics and Maths and worked incredibly hard (I'm not naturally good at maths at all) ending up only with a B for each and an A in Economics. Now, if I had picked Religious Studies (dropped it at AS, got 91%) and Business Studies I'm very confident I would have AAA on my CV instead of ABB. I convinced myself that I wouldn't have received offers if I had weak subjects but when I got to university, it was a very different story. Here are the people's A-Levels I met just from my halls in a Top 20 Russell Group university:
Law student:
-P.E.
-Law
-Accounting
Economics student:
-Business Studies
-Sociology
-Politics
English Literature student:
-Art
-English
-Religious Studies
That's just from my halls. My friends from college also got into Top 20 universities and some of them had Media Studies, IT and other incredibly easy subjects. The whole two years they told me I was mad for taking such difficult subjects and for a long time I ignored them and felt confident that it will secure my offers; which it did... but no more than their offers. We all applied to roughly the same places; big cities like Manchester, Newcastle, Liverpool, Birmingham, Leeds etc. Now before someone says, "I do Religious Studies and it's the hardest evaaarrr!!!!" - no, it's an incredibly easy subject and nowhere near the difficulty of English Literature, Maths, any of the sciences, History and so on. I got 91% at AS for RS and didn't carry it on purely because it's a weak subject. Please don't think I'm being arrogant there; I am of very average intelligence.
I've come to the conlcusion that unless you're applying for a very prestigious Top 10 University, e.g. Oxbridge, Warwick, UCL, LSE, Durham... your grades are more important than your subjects. I very much wish I had AAA in easier subjects because my ABB is going to cause me problems with grade filters and minimum requirements with top companies like the Big 4 audit firms who want 340 UCAS points for a lot of their positions.
So my advice; if you're planning on applying to the big city Russell Group universities, bear in mind that a grade A in an easier subject is going to give you a less stressful time during A-Levels and will serve you better in the future than a B in a harder subject. Of course, an A in a harder subject is the perfect outcome but a lot of people drop a grade. Don't be fooled into thinking that "respected" subjects are paramount, because I have just witnessed first hand how that is not the case at all.