There is no "Best anti spam" script.
Each script, performs it's actions in different ways.
Factors involved in the creation of a script, include, the speed of detection, the complexity of detection, the detection features required.
Each script, is based on a "Speed" V's "Features" system. The more speed, the less features, the more features, the less speed.
You shoudl try out some of the anti spam scripts available. these are listed inside the Tcl scripts archive on
www.egghelp.org