Road trip from Seattle to Las Vegas - best route?

[LocustHorde]

I'm heading out to Vegas in early June and would like to know the best route. Mapquest suggests a strange route of going through Idaho and Salt Lake City. I'm leaning toward taking I-5 to Bakersfield, then the I-15 to LV. Another option is going to Reno, then hitting the US-95 down to LV, but that one seems a bit dangerous, I can't conclude if that road is a two-laner(one way lane each way) for about 400 miles or so..