I've tried both of the major AdBlock extensions in Chrome; AdBlock and Adblock Plus for Google Chrome™. In Firefox, AdBlock is 100% effective, in Chrome there are frequently unblocked ads. Also, ads are sometimes loaded and then blocked, whereas in Firefox they are never requested.
So why is Google Chrome worse than Firefox? The conspiracy theory is that Google's business is ads, but I know that can't be true. The extensions all use the same ad blocking lists, so why doesn't Chrome's ad-blocking extension work as well? Is there one that does?