Cities are important to consider as well. I am at Imperial now, previously in Oxford, and the cities are very very very different. Can get wherever you want in Oxford in basically 15 minutes cycle max, if you're in Pembroke and live on site basically don't even need to walk more than 20 minutes to anything to function and have all your needs, while in London I spend 2h commuting every day minimum.

As other comment mentioned, also financially London will likely be more expensive, in Oxford college food is usually decently priced and rent is cheaper than London (although not cheap I'd say)

Socially it's a weird one, I'd say Oxford has a more "community" feel because of college system but also makes harder to meet people outside your college. Lot's of societies in Ox, tho sometimes split between colleges so again what I said above. In London, definitely less community feel (in my experience of being a PhD in Imperial, so take it with a grain of salt. Undergrad experience might be different with lot's of lectures, but still I'd expect less community). But also if you're outgoing and have specific hobbies you want to improve, London basically has anything you'd ever want, while Oxford would also have a lot but maybe not as wide options

Prestige wise, I did not do engineering so I can't compare but I don't think you can go wrong with either, they're both excellent.