If you want maximum security get a lock that has been independently rated, and gets top marks. The two big rating agencies are Sold Secure and ART. Sold Secure's highest rating is 'Gold', and ART's highest rating is '5 Star', but this is a new rating for ultra-heavy chains, so in reality '4 Star' is excellent security for bicycles.

http://www.stichtingart.nl/sloten_resultaat.asp

http://www.soldsecure.com/search?pro...mpany=&action=