4G (LTE) is faster... that is a plus. What Chevy doesn't say is the data plan cost/requirements. Anyone with a 4G Cell plan realizes that you have to buy a corresponding data plan. So If one uses the vehicle (or your phone) as a mobile hot spot, one needs a data plan that handles all those kids Chevy shows using the mobile hot spot. So just like "On-Star" there is an on-going cost to use. That said, I would hope Tesla will move to 4G soon. I would guess ATT and other carriers are going to move from 3G in the near future, just as 2G has faded into history.
It would be a nice feature in the vehicle. But, I have a 4G phone and tablet and both can become hot spots. So Nice but not Necessary when I get my Model X... maybe 5G by then.