I will also like to add that as a fellow international student (I remember that you are international and not EU I think, not sure though) I understand how hard it is to find information about universities abroad especially when ranking systems are so unreliable. This is what TSR is here for, for people to share their experiences and expertise in universities in the UK. (It is why I joined and looking at the questions you ask, I think this is why you joined as well)
However, asking the same question 20+ times in different threads does not help you understand about the universities any further than personal opinions and sometimes screwed up perceptions of the prestige of university equaling the quality of the course. The crux of the matter is that all the universities that you applied to are prestigious (Although rankings may not display this and there are reasons why St Andrews is so "low"-ranked in global rankings which have something to do with research output and size of university- this is why Brown University in the US is so low-ranked as well)
Look at the courses and the modules that you can take in each university. Each university teaches a course with the same course name in different ways and has different course structures. Oxbridge is the notable example, with its world-famous tutorial system, but some schools offer more lectures or more seminars. Some may even offer tutorials (albeit not as frequent). Because all of your universities are "prestigious" choose the course and the environment that fits you more.
@GermanIRhopeful outlined the uniqueness of the St Andrews experience very well but like he/she said it is not for everybody. Think about what you want to get out of your university experience and stop being so fixated on "prestige" and job prospects because I can assure you that all of the universities that you applied to has excellent job prospects and are definitely "prestigious". What matters more is what you do with your degree (internships during breaks... study abroad... undergraduate research etc...) not where you are going for the degree... especially when all the schools that you applied to are sublime.
Don't apologise, do the research on the universities that you applied to! After all, it is your life and you need to take initiative on where you want to go and what you want to do.
I apologise about any grammar mistakes because it is 4:30 am in the morning here but I thought I would just write this post after seeing all of your posts.