If Mapquest has the times about the same, watch the weather and make the call based on that. We usually take I-80 (Iowa Nebraska route) from Milwaukee to get to the Snowies, but we took I-90 (South Dakota) to Togwotee. Both will be similar interstate driving with the exception of the I-90 route heading through some smaller roads in western South Dakota/Eastern Wyoming.
When we got to Togwotee, some guys from MI had just arrived as well. They had taken I-80 and had fought a snow storm the whole way. We had almost nothing to the north...
Weather.com offers Interstate weather forecasts - they are pretty basic but will give you an idea.
We will be back west in the Snowies Feb 25th!