The USAF is more important because they are the ones that bomb ISIS in Iraq and Syria. They are more involved, whether that be drones or military planes, they shoot missiles, drop bombs, and shoot down enemies, while Marine Corps are much smaller and less important.
The Marine Corps is more involved in the sense that, they are the ones going out to fight in close quarter combat. The Air Force stays as far away as they can, by using drones and planes, like you said. Yes, the Marine Corps is a smaller branch, but isn't it quality over quantity?