yeah imperial is in the uk, one of the top univs there, though there business school is not at par with the likes of lse,warwick.
i agree that imperial has the brand name and prestige, but its not well known for its business school.
pros Imperial: program has a lower cost than the program at washu. potential brand name, have a lot of recruitment events, placement of 93%. ideally placed in central london.
pros Washu: smaller class size. new quant finance track might give you the edge (being a new program). have placed well over the years (97% placement). 1.5 year course, so get more time to look for opportunities and spend summer in the US looking for internships.