Hi, I know im terribly late but i also applied for philosophy and theology this year with offers from durham and st andrews. for me, st andrews is ranking higher than durham rn! I stalked a lot of the dept on philpapers and imo the philosophy dept is great- one former st A professor gave a lecture w/ the royal institute of philosophy on idealism that I went to and I found it really fun. its making a vv good impression on me, and im certain ill firm it if i get rejected from oxford tomorrow xd
I also prefer the small-town nature of st andrews as its very quietism-esque lol. the theology dept at st andrews is also really great. although similar at durham, I feel like the social culture of durham just wouldnt be a good fit for me. im also a POC (arab), so i was worried about similar things w/ durham, but ultimately I expected to find some minorities of unfriendly people at any uni. it is ultimately up to you, but I definitely prefer st andrews for philosophy and theology- not just academically but also in terms of aesthetic (as i, like you, do value pretty libraries and buildings aha) and the general area!
i also like that the degree is 4 years vs durham's 3 years (UK) because that means I can spend longer in uni, which is a plus for me. haha!
best of luck
edit: typos