question about these 80 and 120mm fans..

i was just looking at these LED'ed fans at xoxide and noticed that the 120mm fan is 70cfm and makes 39dba of noise. then i looked at the 80mm ones and they were 32.5cfm with just 28.3dba. now 2 of these 80mm fans would put out the same amount of air as the 120mm and be quieter than it.
how come the 120mm is so noisy for only 70cfm? because my friend has a ystech 120mm fan which is 135cfm with 45dba.. only 5 more dba and double the output here.. whats goin on?
i have fallen out of the circle of information here..

max

ok and i was just lookin at some panaflo fans..
this 120mm panaflo puts out the same amount of air as the above LED 120mm fan at 700 less rpm's and a lot less noise...

does this have to do with the fact that the LED ones are 25mm and this one i think is 35mm?

max

trying to answer all your questions with my best understanding.

-a lot of the LED fans I've seen are cheaply made and dont put out as much air as the better quality fans. They also are a bit noisy but 39dba isn't too bad.

-2 80mm fans will put out the same rated amount of air as the 120mm but since the 120mm only has air coming from 1 source it will be stronger but in a more concentrated area than the 2 80mm's

-YStech fans are quieter than most fans and push a good amount of air. Definitely recommended, and Panaflo is good too.

-25mm and 38mm are the sizes. I think the 38mm pushes more air because the fan blades have more surface area than the 25mm.

i dono 39dba is a bit much to me especially after having a dell for 3 years .. right now im using ~32dba 80mm's and an intel retail cooler in my antec case and thats like border line to me so i think ill go for the panaflo fans.

max

The decibel results of the LED fans might not be accurate. Check the listening room:
http://www.sidewindercomputers.com/sidewindercomputers/tecar.html

That will give you a better comparison.