efficiency ref vs return?

I would ask what is more efficient for CPU?

	void EventKeyF(){
		TrueFalse(ref mainMenub);
	}
	
	void TrueFalse (ref bool Booling){
		if (Booling){
			Bool = false;
		}
		else {
			Bool = true;
		}
	}

OR:

	void EventKeyF(){
		mainMenub = TrueFalse(mainMenub);
	}
	
	bool TrueFalse (bool Booling){
		if (Booling){
			Return = false;
		}
		else {
			Return = true;
		}
	}

well since I know how to operate with ref I love them

For small types the difference between passing by reference and value is so negligable that you really dont need to pay it any consideration. For large types, pass by value becomes more expensive as the size of the type inceases since the parameter data must be copied. If your structures start getting large, consider turning them into classes so they are instead passed by reference naturaly.