Ahh, that's tricky. I don't really know how they compare for those subjects - have you visited any of them? When I was choosing, I was quite torn between Warwick and St Andrews, and various things gave St A's the edge - the 'campus' here is much nicer, I think. I got the impression in Warwick that you can just live on campus, with no need to ever see any more of the area. With St Andrews, it's a lot more real and interactive. I think Warwick was described as 'rural' or something in the prospectus, which, from my point of view, was quite entertaining, because, to be fair, there were a few fields, but it was quite built-up in comparison to what I'm used to =) [Also, St A's is easier for me to get to, and a wiser financial option]
Go with somewhere that you'd feel happy. You're talking good repuations anyway, so I'd take the chance to choose a place that appeals to you in other ways. The only disadvantage with St Andrews is that it's in Scotland, and some people are like, 'Where's that? It's a county in the north of England, right?'... *sigh*