I'm on the East side of WA, so for me 93 is more convenient. Been that way many times, will go again in a week.
After the interstate part, the route is most all 2-lane from Twin Falls to near Vegas, but the road surface is good. There is very little traffic on 93, and only a couple of climbs, none particularly difficult (Cabbage Hill on I-84 is the major climb of the trip.) Most of us prefer SR318 between Ely and Ash Springs.
However, 93 is very remote in places. Fuel up when you see it. And there can be some truly nasty winter weather. Checking the forecast is critical.