How do I choose between innerText or nodeValue?

When I need to change a text within a span element, which one should I use and what is the difference:

var spnDetailDisplay=document.getElementById('spnDetailDisplay');
spnDetailDisplay.innerText=sDetail;

or

 var spnDetailDisplay=document.getElementById('spnDetailDisplay');
 spnDetailDisplay.childNodes[0].nodeValue=sDetail;