Here's a few tidbits on your CO/NW specific questions (this run obviously will be on CO or NW, since you say you need to qualify for CO status).
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by SteveHOU:
If I find a good fare in coach which, metal and carrier has the best coach seating and what is your preferred seat?</font>
Well, on CO you're going to transit GUM to get to SIN, so, you're looking at 777 or 767 and 737 service GUM SIN unless you do the island hopper in which case much more 737 service. Check
www.seatguru.com, but best seats are row 14 in a 737, rows 16 or 32 in a 777 (with 32ABS and JKL being my personal faves on the entire aircraft in coach). Check the web site for the 767 seats.
Seatguru doesn't have NW yet, so you'll have to figure out that yourself. Look obviously for fully reclining exit rows or bulkheads.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by SteveHOU:
If I choose coach will I still qualify for possible EUA on the domestic flights to get me to and from the international gateway?</font>
Yes. Just make sure you are not on a "through flight," which would be rare on a routing such as this one. For example, you would not want to be on IAH-LAX-HNL with one flight number (i.e., IAH-HNL as a "one stop") - you would not be able to EUA UG IAH-LAX if this were the case. Off the top of my head, CO's flight 75/76 into and out of HNL from LAX does not continue to IAH, so I think you're fine. Just watch for this if you go with NW.
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Generally: I've done lots of BF on CO and lots of WBC on NW. I used to think WBC was way inferior, but with recent service cuts to BF, they're about the same in my estimation. If you can get WBC on a NW 747 and get the "good rows" (the former first class seats, on a 747-200 that's the entire upper deck rows 55-57 and on a 747-400, rows 1-4 in the nose cone downstairs) these seats totally rock and I like them better than BF. They are 70" pitch; "regular" WBC is 55" I think. They go almost flat but not quite. They are held for CO or NW elite memebrs and you should be able to get them.
Further, NW's NRT SIN service being on a 747 would push me for this over taking CO through GUM just because who wants to sit on a narrow body at all when you can ride the queen of the skies.
Just my thoughts.