IC is situated in the most affluent part of London and so if you're from abroad, you'll feel very safe.
UCL is in Central London, crime is still low but the area is noticeably different. It's more crowded, noisier and generally less chic.
On the social side, there is a lot more going on at UCL than IC, plus it's more likely you'll be mixing with students from other London colleges such as SOAS, SEESS, LSE and King's as they're close by.
As for career, both would get you an interview so there's nothing between the two.
IC is a specialist science uni and comes with it, a certain amount of prestige.
If you intend to live near the uni, I would choose IC.
Attractions include:
Harrods
Hyde Park / Kensington Gardens
Sloane Square / King's Road
Hight Street Kensington
Holland Park
Knightsbridge
It's an extremely pleasant area to live, especially during the Spring and Summer months.