Mr.Mo's is easily the most popular system atm
Blizz-ABS is going to be really good when its done (most advanced enemy AI I've ever seen planned)
and if you're not afraid to "get your hands dirty" so to say, and work with some actual code, the XAS Hero system (1.5) is the most customizable of all of them
there really is no "best" ABS system, but since XAS is the easiest to customize, 's the one I'm using.
(also, I don't see why your question seemed lazy, all you did was ask opinions, not ask for the scripts themselves)