I went to an event called Euromasters in Germany. It was a gathering of business schools from Europe to take part in some sports competitions. The two British schools were Cass and LSE.
When LSE came out for the presentation of their team, their shirts read the following: Who is Cass?
You know the answer.
I agree. Even though I might enjoy some of Cass' courses more, at the end of the day, having LSE on your CV will be a life long "badge" of quality. Nowhere else in the world do you have prime ministers, CEOs, nobel prize winning economists, world leaders,... come and give speeches. Short term, Cass might make more sense, but long term, definitely LSE.