Oh, no special advantage with straights with scarves, except to say that since scarves are just 25-35 stitches in width, they fit nicely on the straights, as opposed to projects with 100+ stitches, which are definitely helped along with the use of circs cuz with circs the weight of the project sits center in your lap.
Phew. That was a long and windy sentence!
I'd buy that full set but we're gonna be up in the mountains sometime here in May and I'm afraid the set will deliver and sit on my porch. KnitPicks delivery is willy-nilly. You can't bank on when they will deliver.