Cfm is a unit of measure, just like mm or inches. There's no one that's better than the other. Cfm stands for cubic feet of air per minute. Sp is an abbreviation for static pressure, usually measured in mm/h2o. The higher the static pressure the more 'force', it doesn't necessarily mean more air. It means when the air flow is restricted either by objects like blowing air past hard drives, through a dense finned radiator or cooler, pulling air through a filter etc it will be able to continue moving more air than a fan with lower pressure or 'strength'.
An example would be an air filter on an intake fan. If two fans are both moving 63cfm of air, that's what they're rated at in an open air environment, no restrictions. The introduction...