Thank you everyone for your response. They are all very helpful.
Certainly I do not need to clear immigation as my itinerary is SYD-AKL-LAX-KOA, then KOA-HNL, then HNL-SFO. I would have already cleared immigation at LAX.
CO HNL-SFO is actually part of BD award where next flight is SFO-ICN with SFO. I did not separate the bookings out because ironically it is cheaper for me to book HNL-SFO-ICN (18750 miles + cash) then SFO-ICN (30K miles + cash) BD award not even including the HNL-SFO leg.
You are correct that I could have flown CO between SFO-LAS, especially that I am a BD *G. However the next CO flight is at 15:48 and costs like $170 + tax each person. So it is very expensive as well as the transit time is only 1 hour with different PNRs. So any late flight from HNL and I would be in trouble, and then the next flight departs at 19:20pm which is very late not to mention all the change fees involved.
VX has next flight at 16:35pm (ie transit of 1:40) about and only $59 + tax so it is cheaper than WN even with luggage included (we most likely have 1 check-in each person), and I can actually earn points on virgin Australia (DJ) Velocity using VX as well, not to mention cabin layout for both VX and DJ is similar and I had no problems with DJ. But then the change fee really put me off ($75), and also I will definitely need to recheck my bags at VX, which recommends me to check in at 90 minutes before departure. This leaves me with not much room, and will practically throw my ticket away and buy a new ticket if HNL-SFO is late as the change fee costs more than the original ticket. And someone in forum mention about delays at SFO is quite common due to fog.
Hence with all these consideration I have decided to fly WN the first time as I think the transit time is big enough for some delays, and the no change fee was the real differnce between WN and VX. In a way I want to try WN to see what all the fuss is about given that they seemed to be the only profitable airline in USA. I have tried JQ/TT/DD/FD as LCC.
Finally, I am planning to hire a car at Vegas and drive to LAX and then to SFO, visiting all those Premium Outlets along the way, before my flight of SFO-ICN. Hence there is no return flight as such. Not sure if LAS being a zoo means much to me as I am arriving but then I went to SYD-LAX/SFO-ORD Y on QF/AA/UA on regular basis on 2002-3 and I always think LAX/ORD has lot of people, but it did not faze me as I was born and grew up in Asia. Not sure how LAS compares with ORD though.
I will certainly think about EBCI as I will be at HNL and not sure if those HNL hotels have free internet so that I can do online checkin at T-24.