Originally Posted by Michael Cox
Fans with a good CFM will usually have a lower SP rating.
how many fans have you looked at have specs that support that statement? i ask because one class of fans, the delta focused flows, not only have extremely high cfm ratings, but extremely high pressure as well (with extreme power draw and noise to match!). if you are just looking at specs, it seems to be that lower rpm fans will generally have lower cfm and pressure, and that smaller fans seem to have higher pressure (but not always higher cfm) than larger fans, all else being equal. simple example from me, my 60mm delta black label has way more pressure than my 180mm case fan, but probably moves less air overall.
also, i don't think you can compare specs from one manufacturer to another, as they may not conduct tests the same way. not only that, but manufacturer specs should be taken with a grain of salt, so really they are only good for comparing fans from one specific manufacturer.
finally, without testing to prove anything, i would hardly make any decision based on specs when the difference is .28mm or 15 cfm. those differences seem so small as to be insignificant. honestly, i'd make a choice based on looks and price if they are that close to eachother, unless several reviews said yes, this fan is better (in whatever way that matters to me) than that fan.