The A15 is slightly better airflow, but more importantly, it's usage is more universal, being recommended for radiators and case, whereas the P14 will have lower pressure. Both great fans, just gotta be careful what you're doing with them. Used to be all case fans were created equal, but now you can target what you want, quiet, pressure, airflow. Thems the big 3. Average fans get you one of the three, good fans, two, but great fans can give you all three, if you've ever asked why would anyone pay 30$ for a fan, that's why. I wouldn't put a standard off the rack Best Buy branded case fan on my custom water loop. If I could've found great fans at the time cheaper (I have the Noctua IPPM 3000 14cm fans on my radiators, now there are...