My decision tree would be:

(1) are you buying a W fare? If so, its upgradable with your SWU. If you are willing to pop for a W and R space is available, then it is a no brainier, take UA.

(2) If the W is more expensive, then you need to decide if you are going to play the lottery. (If your company is paying, you may not care). I've recently looked at running to asia with the kiddos (I drained my MP account, and have not refilled it since UA is now NOT my usual carrier. ) and checked W on UA. Its running about $500 more than the fares I can get on ANA or SQ. That is $2000 more, out of my pocket. If R were available on ALL flights, I might bite, but while I and the SO are GS, the kiddos are not, and clear at their own status... So given how stingy UA is with R space, its probably paying $2000 for TWO upgrades.

This said, if your company is paying, and you are getting higher than a W, your upgrade chances are higher as upgrades clear by fare type, and you will leap frog the 1ks on W.

(3) If you are not getting a W or higher, then you will get the same mile bonus, and on ANA they will give you an exit row since you are *G. ANA values your loyalty.

If its an exit on ANA or E+, I would take ANA any day, any week, any year. Better food, better booze, better service, and the seats are more comfortable as well. And at NRT, got to the ANA lounge, it blows the UA one out of the water, other than the showers, which are better at UA. So shower at UA, then go to ANA lounge.

SQ will also give you an exit row, but I seem to recall they only will give the exit row on day of travel, not ahead of time. I would check that [Run a search here] if they give at time of booking to *G, then they are as good as ANA, you would just change in ICN or HKG (IAD-SFO-(ICN or HKG)-SIN) rather than NRT. You could also do IAD-JFK-FRA-SIN if you wanted.

[And a note, the $10,000 spending cut off for 1K is designed to try to force folks to fly UA in these situations, despite the lower quality of service.]