The gear drives usually are in blown applications. That I know off. The gear drives transfer alot of harmonics through the motor. The chain isnt so bad but the belt drive is FAR better in that area. Easy cam adj. I run a Jesel Belt and nothing else. My boss jeff on his Chevy Hemi has a jesel belt drive and on his 5 blower motors those are all gear drive.
Replace the belt every season!!