You are comparing two excellent courses here: both universities are very good, both courses are very good, both courses are taught by people who really know what they're doing. You probably can't make a bad choice here. Both have superb library facilities, very good staff, an excellent global reputation.
So what are the differences:
Geography: City is in the middle of London, Cranfield is on an airfield site well out in the country (about an hour's drive North of London, or about 40 minutes by train then half an hour by bus or taxi). The implications of this are much higher living costs whilst at City, moderately higher transport costs whilst at Cranfield.
People: City tends to have a lot of the teaching done by (top level) industry professionals, Cranfield tends to have a lot of the teaching done by world-leading academics based there. So the Cranfield course will have a greater academic focus, and the City course will have greater industry focus.
[I have not attended, or taught on, either course - but I have colleagues at both universities who I have a lot of respect for, and I've had quite a few conversations about the delivery of the course with professors at both universities, and spent quality time on both campuses.]
G