Voltage control PWM fans. Downsides?

[Ryun]

I'm going to be purchasing a set of 140mm noctua fans soon and they provide a pwm model and a standard model. On amazon the pwm model ends up being only a $1 more, but they are going to probably be voltage controlled by my motherboard as opposed to pwm (even though all of the headers are 4 pin).

Are there any serious downsides to voltage controlling pwm fans, though?

 

[Ryun]

Additionally, these were the fans I was looking at: http://amzn.com/B00CP6QLY6

These are going to be used as front intakes. Would anyone have any other recommendations over noctua?

 

[flod]

those should be alright unless you dont like the color

take a look here and have fun with google translate
http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html