Figure out the Cubic Feet of your room so 10 x 10 x ? then figure out how many times you need to vent the room... Then get the filter that is rated for this CFM of air going through it.. From what I have read the filters don't work if air is passed through too quickly so get one rated for the proper flow and you should be good!
EX: I just got the Can Filter 9000 and for Exhaust ( Single Pass ) It needs 46 CFM so I am lucky that I have a small space and 46 CFM vents my room enough to keep it cool and not too quickly to smell (Hopefully, only tested it with a bag of stinky bud so far LoL)