I-15 to I-70 to U191 is definitely the easier route to drive. US6 is windy and hilly and if I were driving a 39' Discovery with a toad, I would definitely opt for the easier route. However, US6 is shorter and more scenic overall if that tickles your fancy. You could also go I-15 to Scipio and then take US50 to I-70, then on to 191. US50 is also narrow, hilly and windy but not as far to travel on that kind of roads as US6 and it cuts off quite a few miles between Scipio and the I-70 exit. But, again if you are looking for the easiest route to navigate with your Discovery, definitely opt for I-15/I-70/191.
Roger & Diana
'03 Alpine 36MDDS