Heathrow's advantage to London is that the Underground takes you to the City Centre. From Standsted however, you can take the Standsted Express Express which is about a 45 minute train ride to Liverpool Street Station. From there you have to transfer to various underground lines. A mere inconvenience but slightly more civilized than dealing with Heathrow. For the time being Immegration through Standsted has shorter lines too. If you are considering EOS the upgrade time is alot quicker than AA.