The strength of the gravitational forces between two objects depends on
the masses of both objects and on the distance between their centers.
I don't think you can say that one or the other is the "main" influence.
-- If each mass is multiplied by ' k ', then the forces between them are
multiplied by ' k² '.
-- And if the distance between them is multiplied by ' k ', then the forces
between them are divided by ' k² '.
Seems pretty equal to me.