What is the best airline travelling from Perth to USA Destinations?

What is the best airline travelling from Perth to USA Destinations? I see Cathay as my best option with only 1-stop to Chicago (ORD) PER-HKG-ORD.

Rather than 2-stops on Qantas route PER-SYD/MEL-LAX-ORD or PER-SYD-DFW-ORD.

I would look at Air NZ PER-AKL-LAX

Or to avoid LAX, PER-AKL-SFO?

The only one -stop I could think of is on QR via Doha. 

Make that 2: via HKG on CX. 

Yes, especially when you get the new business class on PER-HKG and also from HKG-JFK/SFO/LAX/many other places. The new J class is awesome.

I believe EK flies to LAX,SFO, SEA, DFW, IAH, IAD and JFK from DXB.

So that's another 1 stop option from PER.

CX flies to JFK, ORD, SFO & LAX. So really it depends on where in the States you're going.

If you are going to Chicago, Cathay Pacific is the best option for you but it won't be the cheapest one. I think Emirates or Etihad fly to Chicago via their hubs, Dubai and Abu Dhabi, respectively.

Flying with qantas would be your quickest option I imagine, and sometimes the cheaper one too. PER-SYD-LAX or PER-SYD-DFW with merely a 1:30hr stop over in SYD, or 4hr stop over if you like to lounge :)

Depends on where in USA you're going, what class and what status you have with which airline?

If you're heading to LAX/JFK/DFW, then I'd say QF is the best, especially on an A380.

AirNZ comes a close second for LAX, but then again, I'm going ex-CBR, so I'm already kinda on the east coast.

As far as I can see, It doesn't make sense to fly through Emirates or Etihad, because you'll have a long flight to UAE, and then an even longer flight to USA, unless if you go through/over Europe, but I still think it'd be better to go QF/AA.

(I may be biased though, as I am a Qantas Platinum.

Cathay via HKG earning QF points. 

Or QF if you're Platinum through SYD just for THAT lounge

Depending on where you are going the overall travel time can be shorter by going via DOH or DXB on QR or EK.

EY isnt an option as there are no flights ex-PER yet.

Another (BAD) one stop option is using SA via JNB but only good if you want to stop in JNB.& as long as you go to a city that SA fly into (e.g. NYC)

The OP stated he was going Perth to Chicago and preferred a one-stop service. Best bet seems to be Cathay Pacific or Qatar:

 QR901 ex PER 23:00  arr DOH 05:20 (+1 day),  QR991 ex DOH 08:00 arr ORD  14:30, duration 28:30 hrs

CX170 ex PER 23:55  arr HKG 07:50 (+1 day),  CX806 ex HKG 11:55 arr ORD 13:50,  duration 26:55 hrs