[@Skepic]Guess why did I start this questionnaire to begin with?
:lol

And yeah, Strike Witches likely have better torque to weight ratio. As unbelievable as it seem they also carry heavier weapons.
The one advantage Griffon Riders have though is that the soldiers can turn around and aim better than a girl on a flying boot-engine.
Think of horse archers except now they are armed with SMGs and rifles.
Though range could be an issue. Also griffons are considerably larger targets.