Looking for great battery life and, secondarily, as strong of a screen display and other features as possible, how would any of you compare the 490s (4K not available), 495s and X1C7 and/or X1C6?  Any others that should be added to that comparison?  Usage is all business (but heavy usage there with lots of tabs, .pptx and heavy outlook (no gaming).  I currently have the 550S dual battery and it's been great...but looking to go lighter and smaller.