The stock on is tuned to a specific range and as the pulley gets older the rubbers gets harder and becomes less effective while this is an adaptive balancer. At higher rpms I think it more effective.
You can't compare this one to the stock one. I don't think there is anything wrong with the ASP or UR UD pulleys for stage X and below.
Here is a good test for yourself. Get to stock balancers and test them.