You asked for advice, so here it goes:

Why not being an elite member of both OneWorld and StarAlliance.

If you fly twice to SIN on J youŽll be UA Premier Exec *A Gold. Eventually three times in J could even get you 1K (!), with the proper routing. When flying SQ send your miles to your preferred FFP and have your J points sent to SQ KrisFlyer program (just the points, not the miles)

Accruing miles in both alliances and making you an elite in both gets you the best of both worlds - easy to redeem miles, when one hasnŽt availability, certainly the other should have .

Putting all your eggs in one basket makes sense for those with limited travels, others... know better