Question about driving directions from San Fernando Valley to Las Vegas, specifically Highway 18?

So I'm going to drive to Las Vegas, which I've done several times before. I was going to go up the 14 to the Antelope Valley, then take the 138 east to the 15. However, looking at google maps, it appears that the 138 dips south and goes out of the way around Llano, while the 18 appears to go more direct to the 15. I don't remember seeing any cutoff for the 18 in the past (not that I was ever looking for it). So should I just forget about this 18 and stay on the smarter, possibly faster (but out of the way) 138, or should I venture on the 18? Anyone ever do it?|||I live in Riverside, but once drove from your area to Vegas. I took the 138 to the 18. It was nice scenically and easy. But I checked google maps, and they recommend taking the 210 to the 15. Depending on what time of day you're leaving, this may be your fastest route.