exhaust fans

the grower wants to know, whats the difference between:

http://www.homedepot.com/webapp/wcs/...ctId=100067594

and:

http://www.homedepot.com/webapp/wcs/...ctId=100396559


which would be better for a x8 26 watt CFL grow(for veg) then 400hps for flwr in a 4'tallx3'widex2'deep box with a 3" passive intake?


or will this smaller guy be enough to get the job done?
http://www.homedepot.com/webapp/wcs/...3+90401+500023


ORRRR

would the grower just be better off with a PC fan?



thanks

those will work the only difference is the cfm really the one has 250 cfm the other has less they will both work and will work better than a pc fan

thanks. so is the 4"er enough, or should i get the 6"?
the idea right now is to install the fan inside of the box, into a pvc reducer to a 3 or 4" 90 deg elbow. not too sure if they have PVC reducers big as 6" though.

In that type of fan go with the 6" its easier to not run the fan then not being able to vent enough IMO

point taken. thanks

I read somewhere that the intake hole needs to be twice the size of the exhaust hole...

I got a 3" PVC elbow for my intake, should I go bigger?