Last winter we trekked from So Cal to the Florida panhandle. Traveling east we took 10. West 40. Both routes have potential advantages. And issues. Our challenge last year was the wind. Get a good weather app and check it at least daily. I'd suggest the real issue confronting you aren't the grades you'll encounter, but the traffic once you hit Cal. If that is a concern, and it definitely is for me, read on. 10 has you passing through the very heavily populated areas from Redlands until north of LA - and I don't mean Lower Alabama! If you elect that route, access 210 just west of Redlands. It will add a few miles but subtract lots of traffic congestion. Even at that, time your travels between commuter traffic times.
40 will allow you to bypass the traffic issues. I'd also suggest you consider the following RV parks if they are close to your daily mileage travels. East of Kingman, Arizona, Blake Ranch is outstanding. Bakersfield has a number of great parks. Orange Grove on 58, Bakersfield RV Resort (with an excellent on site restaurant) & River Run RV, provided in the order you will encounter them, are all top notch. My next stop would be Betabel RV on 101 between Salinas & Gilroy. Once again, time your arrival in Santa Cruz between commuter hours. Use 129 to access 1 from 101.