I hate LAX, but in this case, I would fly into it because of the direct flight benefit. Also, if you are delayed/cancelled, there's probably better flight opportunities to hop to vs. the limited offerings at (my two favorite so-cal airports) LGB and SNA. Definitely hire a car, the rental car shuffle is atrocious.
I'll add, if you miss a connection in PHX, you'll likely end up driving the final leg to so-cal (6hr drive), or pay the walk-up fare for Southwest into any of the 5 local airports. Not terrible, but kills half your day (driving) and you probably weren't planning on it.