Imperial College London OR UCSD?

Please please help me to decided! I am a high school student in China and I just got the offer form IC, material science and engineering, and UCSD, applied mathematics in Marshall College. I've never been to other countries before...

I've heard that British foods and weather were extremely terrible people will easily get depressed there, but I quite like the old buildings, streets and the historical and cultural atmosphere there. For California, I know the weather there were the best in the world but actually how good is it? I've watched some videos, is it located in a countryside near a beach??

I'm really frustrated when considering which uni I should go. I believe both of them were the top uni in the world. IC was my dream school since I study British alevel courses, but I'm not sure now...