The difference between this one and the white (without the "CO") is that the company has made some improvements for greater durability. Specifically, they advertise it as continuous operation.
According to specifications, it is slightly quieter, but in practice, there is no difference, it is equally quiet.
Very convenient and here is the ability to connect the fans in a series.
Absolute value for money as well.

Silent and no difference in cooling. I used them to replace the factory fans on my deepcool captain 240. It simply doesn't move as much air, but no biggie. I haven't noticed any difference in performance when overclocking my i7 920 from 2.6 to 3.8.

Also, the daisy chain they have is incredibly convenient.

I highly recommend them.

Simply fans do their job as they should, they are cheap with PWN, PST technology and they are worth less than 10 euros.