Question is how often do you foresee you will fly on UA. UA elite members get free upgrade to economy plus, which should be much emptier than normal economy. Although the recent changes to the program have put me off, but still better than crediting to Krisflyer for me (unable to get any meaningful redemption before mileage expiry). Even silver gets you free upgrade to economy plus at check in, which is quite a bit of value too.
As for elite status, the question would be how often you fly on star alliance. I've gotten mine with A3 (program just changed), even though I only have 1 to 2 trips a year. Lounge access is quite a blessing, esp on airlines like UA (eat until full just before boarding). Same for the other benefits like extra baggage, priority queue etc, especially US departure (domestic or international).
I would only fly to US about once a year.
UA/NH has a duopoly on SIN-NRT-IAD and prices are similar (about $100 apart). Their prices are about $1600+ for K fare during off-peak season. To even get UA Silver I need 25k miles per year which I would not qualify since I would only earn 20k miles or less. I would have to fly another 5k or more miles on 100% mileage earning fares which would be quite expensive. I also wonder what are the chances for upgrade to Economy+? UA has tons of Elite members, it's like an LV bag, everybody has one.

If I was to credit mileage to UA, I would fly NH. If I was to credit mileage to OZ or TK (for status) or SQ (for miles), I would fly UA.
So if for example I credit the mileage to SQ with the 3 years expiry, I would probably earn around 60k miles by the 3rd year which I can combine with the miles from my CC spend a redeem a mid/longhaul. My miles comes from my CC spend, not by flying (100% mileage earning tickets are too expensive).
Within Asia I'm currently flying MH due to the very low pricing and I still earn 50-70% miles on cheap fares. As for OW partners, only BA have good pricing to IAD at $1800+, but earns only 25% mileage to MH.
As I fly purely for leisure (I don't fly for work), I would go for the cheap/affordable prices. MH is working fine for me so far. I thought about CX but mileage and status earning tickets are too expensive.
