If your flying will *terminate* in SFO or LAX, the former is a much better option as immigration & customs and transfers into the city w/o renting a car are much better.

On the other hand, if you are planning on *changing to a domestic flight* from your international flight, LAX is the way to go. While it is possible you will have to change terminals, there are *many* more flights...and you are MUCH less likely to be weather delayed. SFO is notorious for weather causing delays on departures.