Should I avoid updating transform/GameObject variables if they haven't changed?

I have objects that respond to changes in global state (typical state-based design) during the call to `Update`. I'm wondering whether it is efficient to always update the values, or whether I need to cache the values and only update those that have changed.

For example, in pseudo-code, can I simply do:

Code (CSharp):

1.  
2. var newPos = getStatePos();
3. var newRot = getStateRot();
4. transform.SetPositionAndRotation(newPos, newRot);
5.  

Or should I be doing something like:

Code (CSharp):

1.  
2. var newPos = getStatePos();
3. var newRot = getStateRot();
4. if ( newPos != curPos || newRot != curRot ) {
5.     transform.SetPositionAndRotation(newPos, newRot);
6.     curPos = newPos;
7.     curRot = newRot;
8. }
9.  

The same question applies to things like material.color, or basically anything else that can be changed. Does it cost anything to set the same value again and again?