Burn speed is somewhat of a gimmick for drive manufacturers. Whats most important is burn quality, so for me, my 20x burner only burns at 12x because thats where the media produces the lowest error rate. This will ofcourse depend on the drive and the brand of media being used. Also the time it takes for a burn to complete is not always directly proportional to the burn speed, it depends on the writing strategy used by the burner. For a while 12x was faster than 16x due to the writing strategy of the drive.
As for fastest reader, you can check out the reviews that cdfreaks does on new drives, they are usually pretty detailed.