It's really two different features (snow/ice setting on the terrain response, and low/hi transfer range selection).
You would make the decision to use each of them independently. So, if driving in snow/ice then you use that selection on the TR, if offroading on hilly terrain you use low range. If offroading in snow/ice conditions then you may be using both, as Houm points out.
In general, for driving on-road in snow, I see no reason to use low range. You want a higher gear when launching from a dead stop in snow to prevent wheel spin. The Terrain Response snow/ice setting handles this well by delaying throttle response and adjust shiftpoints, and reducing intervention from the traction control system.