How do you find height of an object

I am making an app with C# and NGUI. In order to make the app work, I need to find which object is lower. How would you find that, in c#? This is my code:

using UnityEngine;
using System.Collections;

public class NewQuestion : MonoBehaviour {

public UILabel aText;

public UILabel qText;

public UISprite qaSet;

public UILabel aButton;

void Update() {
	
	Debug.Log ("aButton height: " + qText.height.ToString () + " position: " + qText.transform.position.y.ToString () + " Total: " + (qText.height + qText.transform.position.y).ToString ());
	Debug.Log ("aButton height: " + aButton.height.ToString () + " position: " + aButton.transform.position.y.ToString () + " Total: " + (aButton.height + aButton.transform.position.y).ToString ());
	Transform aTransform = aButton.transform;
	Transform qTransform = qText.transform;
	if ((qTransform.position.y + qText.height) <= (aTransform.position.y + aButton.height)) {
		qaSet.bottomAnchor.target = aTransform;
		qaSet.bottomAnchor.absolute = -32;
		qaSet.bottomAnchor.relative = 0f;
	} else {
		qaSet.bottomAnchor.target = qTransform;
		qaSet.bottomAnchor.absolute = -32;
		qaSet.bottomAnchor.relative = 0f;
	}
	qaSet.ResetAnchors();
	qaSet.UpdateAnchors();
}

}

Thanks!

Edit:

What about how to change the height (this time the from-top-to-bottom height). For instance, how would I, in a script, change an object to be half the size of the room? What if I want to make it the same size as another object?

You substract the two vectors and compare if negative or positive.