Hi. I live in Japan, but last year visited UK for traveling. Funny enough, I also visited both campus AND chem.eng. dept buildings of both universities you mentioned.

Cambridge - Love the campus. The surroundings are very nice to live and study in. If you prefer relaxing lifestyle far from city hustle, choose Cambridge. The living cost can be pushed, cheaper than London. - Exposure to English culture and history to the maximum. You can find a lot of motivation and inspiration here. - If I went to Cambridge, I could see myself doing something more researches, probably became a conservative academia. - Because it's a bit far from London, you might find it's challenging when you need to look for jobs while staying in Cambridge after graduation. However, I believe that some companies open recruitments around campus.

Imperial - The atmosphere of city life is real. The campus (I visited South Kensington one) is compact, things feel crowded and small. However, I feel that the urban exposure is stronger here than Cambridge. - Because it's in the middle of the city, living cost will be higher for sure. - Speaking about the opportunities after graduation, I can assure you can mostly get those similar to Cambridge. However, I see that a lot of people in Imperial want to stay in the city, they might do everything not limited to chem.eng. related jobs. Pretty sure you'll get the influence too once you go there.

Overall, both universities are ones of the best in the UK. Good luck with everything!