Which is better?
Oxford or Cambridge or Imperial London in terms of CS
They are so closely ranked, across so many ranking bodies, that there is no helpful answer. Read the detailed info that is available online on how the courses are structured and figure out which one sounds like the best for for you. You can only apply to 2/3 of them, & your real challenge will be getting in.
And if you were thinking of Fall 2020 you’re too late, deadline for Oxbridge was October 15 as well as registration for MAT/TMUA.
Do you have the qualifying AP/IB subjects and scores?