Just did a flight to NZ and back through the States. I would not recommend taking the 2 hour transit option in either LAX or San Fran. It is barely enough time to get through all the hoops they make you jump through. There are major works going on at LAX, they don't offer any assistance or sign posting to help you navigate their shithole of an airport. So after having to go through customs check, get your checked in luggage, re-checking it in 20 metres later you have to hope you get through security with everyone else, not just the people from your flight, on time. Only the US make you do all this and they simply don't have the facilities/resources for it. At San Fran, one of their runways is shut down. So while the airport is nicer you can end up stuck on the tarmac waiting for a gate like I did, losing 50mins. Security was a quagmire and after finally getting through I was told my gate was closed, boarding finished. I ran anyway and they let me on, closing the doors behind me, stranding around 30 people from my previous flight and, as I found out later, my luggage.
Got a nice comparison between United Airlines long haul and Air NZ. The interior of the UA planes just feel a whole lot more plastic and cheap compared to how the Air NZ planes are fitted out. More leg room on the Air NZ planes too.