Hey Yimi1995,
Congrats on your admissions!
I think it would be completely personal choice. But if I were you, I would chose Imperial over Rochester, giving in to the reputation Imperial has in Europe. Having such a reputated uni on your resume in London, which is a finance hub would broaden up my chances with landing in a job.
The only advantage I will be getting in the US is able to search for a job for 3months without any legal issues, if I get one, then I can stay for another 29months, without a sponsorship. Though Rochester is not a bad uni but it ain't one of the top in the US like Imperial is in the UK and/or Europe.
But, from what I hear top companies in the UK don't mind sponsring for the right candidates from ICL.
Good luck!