A note on the "which college shall I apply to" question. The short answer is:
"Don't worry, just pick the one you like, and be aware that approximately 25% of successful applicants to Oxford are placed at colleges they did not apply to".
The long answer is below.
Being collegiate universities is the core characteristic of Oxford and Cambridge. When I say collegiate, I mean
really collegiate: the colleges are the academic hubs of those two universities.
A college is a lot more than a hall of residence. It's a self governing academic community. Regardless of its age, its size, its wealth, its beauty, its ability to win rowing races, how good or bad the food is, how cool or uncool the bar is, and how often it holds a ball, each college is fundamentally about the pursuit of academic endeavour.
College choice appears to (sort of) matter, but it also doesn't matter at all.
Whichever college you go to, you will face the same sort of workload, you will have the same chances to party, put on plays, play sports, and do politics, you will have the same chance to make lifelong friendships, and at the end of the day you will get to write BA (Oxon) on your CV, or on the title page of that killer academic book you have just written. Wait a few years and you can write MA. If the book was your thesis, you can write D Phil.
When you become old (this does happen), you will either remember your college with love, or not think about it at all. If the former, you may well turn up at your college once every five to ten years in a dinner suit or ball gown that may feel a bit tighter than it used to, eat a good dinner (with great wine), listen to the Warden/Master/Provost/Rector/President/Principal give a speech, and then party till dawn like you were still nineteen.
If you have any money, you may send some to your college, so that others can have what you had. You may hope that your children go to your college, but will be happy if they go to another one, or a different university altogether.
The fact that you had never heard of your college until the day it offered you a place won't change any of this.
Which is the best college in Oxford?
The answer, almost invariably, is "the College of which you are a member".
The video attached takes a light hearted approach to the question -
https://www.youtube.com/watch?v=inYEXUjh2cYMiss S Byng MA (Oxon)
(As Parson Woodforde once wrote: NB: a Wadhamite)