Display:

$\stackrel{\‾}{x+y+z}\text{versus}\stackrel{\‾}{x+y+z}$

Source:

<mrow>
     <mover accent="true">
          <mrow>
               <mi> x </mi>
               <mo> + </mo>
               <mi> y </mi>
               <mo> + </mo>
               <mi> z </mi>
          </mrow>
          <mo> &OverBar; </mo>
     </mover>
     <mtext> versus </mtext>
     <mover accent="false">
          <mrow>
               <mi> x </mi>
               <mo> + </mo>
               <mi> y </mi>
               <mo> + </mo>
               <mi> z </mi>
          </mrow>
          <mo> &OverBar; </mo>
     </mover>
</mrow>