Using policies vs subscription listeners

I am trying to understand if there is any detrimental effect on the system if we are to use subscription listener workflows instead of policies (reference doc vCloud Director 5.1/5.5 blocking tasks and notification package using AMQP ). What I find appealing in subscription listeners is that they can be built up and started on the fly and we would be able to get away from managing policy templates. But there is a concern over utilizing waiting event on over some hundred plus subscriptions. Does anyone have any positive/negative experience to share with one or the other method? Thanks,