84 is a bigger road but also has more traffic. That does two things, one it beats up the snow on the road and makes it more challenging, the second is there are more other vehicles around to do dumb things and ruin your day for you. While 17 is a bit isolated in spots it's a good road and with less traffic should be fairly easy to travel on as long as it's not icy. I'd leave super early, like 5am, to get out ahead of it because once she pops north of 17 and is on the small roads things can get dicey in a hurry.