[syswizard]

Systems are great because they take the emotion and "second guessing" out of the decision making. This greatly reduces the stress associated with trading. The downside is the meager performance and huge drawdowns that can occur. Just ask Ryan Jones ("The Trading Game") who embarassed himself in a trading contest a few years ago with his "pullback" system. Also, John Henry's performance past few years has been nothing short of embarassing as well.
Systems CAN work under certain circumstances like special "events" like break-outs, gaps, etc. where there are literally hundreds of trades to manage in a day. Where systems are really at a disadvantage: swing trading index futures for instance. Just one person's opinion.