Pros: PWM, High static pressure, Good flow to noise ratio
IMO, these are best use with a PWM splitter like the Akasa Flexa or Smart Splitter. As they allow you to control multiple PWM fans with one CPU PWM fan header without worrying about overloading your fan header as they supply their own power to the fans. Then you can control basically all your radiator, or even case fans, based on your CPU temperature.
Here is a picture of my Vipers on my 200mm radiator with a custom made plenum.