Gears will be usefull very situational.
I guess they consume different levels of energy.
If G2 consume 10 Energy Units (random numberation), G3 i guess consumes 25 Energy Units, G4 goes up to 100 Energy Units and Awakaning goes 500 Energy Units.
So if possible to fight with G2, he will always prefer that, since it consumes way less energy. He will increse the amount of Gears, depending on the need.