Well, I'm not saying that King's isn't a good uni. King's is good: its Institute of Psychiatry is well-known world wide; it has great depts such as English, French, law, American Studies, War Studies, etc.
You can argue how superficially similar UCL and King's are, but you can't change the fact that, academic-wise and location-wise, UCL is better than King's. As The Sunday Times 2005 University Guide describes: "UCL is physically and academically at the centre of the University of London."
I'm not saying, though, that one should pick UCL over King's. It's subject to individual preferences. After all, some like it hot, some don't.