Well I would defo say keep on looking at the specs for the subjects, and really deep the fact that you're gonna be doing that for the next 2 years. A-Levels are hard period, but think about whether this subject will give you any motivation at all, or whether you'll want to either pursue it later, or if you'll use it in your life in general (it helps you to understand society, the world, etc)
And Philosophy while very interesting (I do it, as part of RE), is focused a lot on God, and people less, whereas Politics is people more, God WAYYY less, PMs and Presidents seem to be god there 🙄😂
So think about that, do you want to learn more about God and moral attitudes in society (which is really interesting) or the institutions, words and events that have knock-on effects in society?