I would pick I-40 over I-10 any day. It's much more scenic in my opinion.
The last time I drove home from Houston to So Cal, we went out of our way to climb north to get to I-40, just because I couldn't bear the boredom of driving I-10 again.
When I was a kid we would take big trips every summer (L.A. to Nova Scocia, L.A. to Key West, etc.). Dad would always start the first day of the trip at 3:00 am to get as far as he could through I-10 in the dark because is was the most boring part of the trip and because he didn't want to drive our truck in the heat of the day. He would turn us north once we got someplace interesting, and then the vacation would begin.
Have a great trip. Sorry you don't have more time to chew the scenery.