Welcome to the forum Jackie Brown. This is one of the great debates of the internet, just like Lion vs Tiger, Great White Shark vs Orca, and Hermes vs Gucci, and Star Wars vs Star Trek.
You can read more in this dedicated thread about which city is better.
http://sleepny.lefora.com/2009/07/08/london-v-new-york/
What is your opinion? I believe that London as the World Capital comes from this article in the Evening Standard (An English paper) referring to an article in New York Magazine way back in 2007 - all posted by Brave here in this thread.
http://sleepny.lefora.com/2011/05/25/london-is-the-capital-of-the-world-says-new-yorkl/