I'm biased as a BD*G but I would go with BD.

Firstly, BD have a regular run to Moscow (some codeshare with Transaero that only gives destinations miles, but also some operated by BD that give status miles too). BD performed very well in a recent survey by the top UK consumer magazine Which? for its long haul flights. Though MOW LHR is medium haul the service is still quite good.

There are many one-stop BD status earning options to NYC with *A from MOW. For HEL and ARN you'll probably find it convenient to use SAS and again that gives earning on BD. You can collect destinations but not status points internally on some Transaero flights too, if you want to switch from SU.

If redemptions to NYC are very important, BD are pretty good at getting flights on other *A airlines and they would also offer redemptions via LHR with Virgin (not *A but a BD partner) to JFK. Though this is not quite as economical on points as a *A carrier, it would be one stop. You can also claw back some points by as you'll only be charged economy on the LHR sector on BD metal. You'll also get four upgrade coupons per year for any BD flights that you need to buy with cash.

BD lounges are fine at LHR and you'd access *A most other places if you get to BD*G.

Last but not least, its a lot easier to reach BD*G than to get *G with most other *A carriers. You need 54k to get *G but only 38k to keep it. I assume your MOW-SIN-HKG trip will allow you to travel back with a *A airline (TG or LH) or that you are going back via SIN with SQ, so that will get you to 22k and each LHR trip will get you 4700 in flexible Y (1.5x) so you'll easily get your first BD*G in a year and if you keep travelling to London you'll have no problem keeping it.