As stated, the front of the usually is the input side & the rear is the exhaust side. The air is suppose to be pulled that way.
Their is a big difference in airflow & noise level on the fans. Look at the RPM level, CFM, & dba rating. This varies from company to company. Some smaller 60 mm units will make more noise than an 80 mm fan.
I have bought several different brands of the same size till I got the brand that does not sing to me!