PerfectDisk v7.0, I liked the O&O v6.5 GUI better but did not like the hidden service it would run consuming memory, if I disable the service it fails to function, and O&O also had issues with the firewall. PerfectDisk has "smart defrag" which defrags accoring to how often certain clusters are accessed, whereas O&O has STEALTH, SPACE, COMPLETE/ Name, COMPLETE/Date, COMPLETE/Access. My guess is COMPLETE/Acess would be equal to smart defrag.