Arctic P8 PWM vs P8 Slim

Nowhere have I found someone comparing these. Looks like the P8 Slim is their new model which got a lot of praise, but I also have the room for a standard P8 PWM. Which is more quiet and effective for pulling on a radiator?

I would use it as a dedicated idle fan on top of my gpu pull through cooler so it wouldn't have to spin up its fans at idle levels.