Fans don't cool, they move air.
CFM represents the max volume that can be moved by a fan at max speed without any restriction.
think of it as HP for an engine. engines also have torque value. in fans it would be Static Pressure which defines how good the fan at overcoming airflow restrictions.
And of course there is a noise and RPM factors.
So to decide which fan will suite your needs, it would be helpful to answer questions like
where the fan would be used (on a cooler, on a radiator on a case)?
how much of airflow restriction in that environment ?
are there noise preferences?
what size of the fan is required?
how much it should cost ?
some people would consider color and lightning options of the fan.
with all that info, you can make a new thread and someone will help you.