Originally Posted by
mlshanks
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.
http://www.lawa.org/welcome_LAX.aspx?id=246 is one of many sites with LAX terminal maps. UA's Web site showed yesterday's flight from SYD arriving at Terminal 7. OP may depart from 7 or 8 (I thought 8 was just commuter jets but am not sure). I believe Terminals 6, 7 and 8 are connected by corridors (you don't need to go outside and it's not a long walk; they should be able to hand over any checked bags at a transit desk outside of Customs). At either airport they'll have to go back through security to their domestic flight date once they depart Customs and hand over their bags to a transit desk. Should be no need to go to the check-in counter.
SFO is indeed more compact. OP didn't ask about variety of onward flights, in case they miss their original connection, so maybe that's not a concern, especially if they're continuing on to a city with several UA flights that day.