My vote goes to WinPatrol because it is more user friendly and easy to configure, if you add advance registry monitoring it is very effective.
Malware Defender is a good product, if you have the time to get everything setup correctly it is more stable then Online Armor and Comodo, bugs are at a minimum and never loses its settings when upgraded
MJ Registry Watcher is also good, but not as user friendly as WinPatrol.
Thanks.