Looking for advice on taking the I-10 v. the I-40 from San Diego to Virginia. The 40 adds about 10 miles (negligible). Scenery? Is one interstate more well-traveled and populous than the other? Given that this will be in the middle of August, is the 40 appreciably cooler than the 10? The 10, from my recollection, is quite flat (which I don't mind, as it's easier on a car); how mountainous is the 40?
Thank you! :)