For my PhD, should I go with the more prestigious university, or the one that is a better research match? I will be starting a PhD in computer science in the UK this year, but have to decide between two offers that I'm pretty torn about. I've communicated with the supervisors from both universities in detail and contacted current graduate students there, and feel I have all the information I need, but am still struggling to decide.
University A has a very reputable department with a lot of academic staff and graduate students in it. The academic community here seems bigger and more vibrant than I am used to, which would be a big learning experience. At University A, I would be funded to work with a younger supervisor who's pretty early in their career and who can offer me more office hours due to less academic duties. However, our research interests don't align as closely.
University B's department is also of a very good standard, but is less prestigious than University A's. It is also significantly smaller, both in terms of staff and students. I have previously spent 1 year at University B and know that the research being conducted there is a closer match to what I want to work on. The supervisor here is more established and is well-liked by the community, but has more academic duties.
Funding from both places is comparable and I believe both supervisors would be good mentors both academically and personally, so the two options seem to be equal on these points. Even though the student community is very important to me, I would be willing to sacrifice the better community at University A in favour of working on my preferred research at University B. What I am more hesitant about is whether choosing the less prestigious option now will hurt me in the future when looking for jobs (ideally, I want to stay in academia). I'm under the impression that going to the more well-known institution would put me in a better position and provide me with more options when applying for postdocs.
I appreciate that I'm very privileged to be in this position in the first place, and am thankful for the opportunities in front of me, but I've been thinking this over for weeks and still haven't made up my mind. What I find the most scary is that it feels as though where and with whom I do my PhD will stay with me for the rest of my academic career. I would appreciate any feedback from people who have been in similar positions in the past, and/or tips on what I should prioritise when making my final decision.
Thank you!
If you want to stay in academia, your top priority should be producing excellent research.  From your post, it sounds like this will be possible at either university.  Another helpful factor is your academic advisor.  Ideally, you can study under a very famous/well-respected/talented person.  Again it sounds like you have two good options in this regard.
If I may, it sounds like you have two good options.  This is a positive to me in that you cannot 'screw it up' and make the wrong choice.  One piece of advice is to consider the process of obtaining your degree rather than what happens when you're done.  You're looking at years of effort, so why not try to enjoy/maximize it instead of fretting about ultimate placement?  Live 'in the moment', as the millennials like to say.
A last cliche bit of advice is to flip a coin.  Heads = A, Tails = B.  Once you see the coin land, you'll either feel a quick sense of glee or sting of disappointment.  Then ignore the coin result and pick based on this feeling.  Good luck!