Okay, so first of all, take any advice you see on this forum as a caution because it's plagued with STEM students who stick up their noses at any kind of *gasp* social science *gasp*.
And besides that, people greatly misunderstand what 'soft' and 'hard' subjects are. They are not concerned with the difficulty of the subject, although there is a correlation, but instead wirh how facilitating a subject it is i.e. how many university courses it opens you up to. The reason people class sociology/politics as 'soft' subjects, is because they are generally not as facilitating for as many university subjects as say maths is.
To explain a bit more, the reason a subject like pure philosophy would be more facilitating than sociology is because the main focus upon philosophy is not trying to cram lots of information in your head, but instead about accurately presenting arguments and evaluating viewpoints. You can be very vague in sociology and get away with it whereas you cannot do that in pure philosophy. It's not to do with difficulty, but how the subject is typically geared.
As to whether it matters; really depends on what you're going to apply for. If it's a highly competitive course like law I would advise to choose more facilitating essay subjects (philosophy, english literature,languages, history are the main ones), but otherwise it shouldn't matter. I got offers from all the unis I applied for and all were RG and I have an A-Level in Sociology.