One huge advantage of your planned route is that it takes you by Guadalupe National Park and Carlsbad Caverns. Another cavern that is pretty amazing to see is also along your route the Kartchner Caverns near Tucson.

It is easy to also drop south of I-10 and check out the famous Tombstone area (http://www.roadtripamerica.com/places/tombstone.htm)

As to whether or not you continue on I-08 to San Diego or use I-10 thru Phoenix and into San Bernardino County -- it really depends on where you are going in Orange County. Palm Springs is a huge Spring Break destination and it is on I-10.