I have been looking at target stabilizers(24"-36") for 3-D. I want to know what advantage or disadvantage there is to the flex of them? Some I have tried have no flex and others are like a wet noodle.

You will just have to try them with your bow and see how it works. It's mostly about balance at full draw. How the stablizer reacts after the shot really shouldn't matter, the arrow is already gone. I would pick the one that "feels" the best to you when you shoot it.

A longer stabilizer simply lets you hold more steady at full draw. It may take longer to settle down, but once it does it adds more resistance to side to side movement.

They also make nice bow rests while your standing around talking to people.

Paul