This debate can go on and on...
I could be biassed as I now live in SIN and I'm an SQ PPS member. However, I gained this in just six months. This entitles me to First Class lounge when travelling J and Silver Krys lounge when travelling Y. Discounts on in-flight duty free, invitations to member-only events, all sorts of "lifestyle priviliages" (never used them!) blah blah. Point is that this tier is very achievable.
For me, my employer has a deal with SQ so I have no choice over airline. As a first time Star Alliance member, and after living in Hong Kong and having a great relationship with CX and Marco Polo, I think I would always, where possible, have a relationship with the home carrier. You can often conver your membership under corporate deals so if you do move (location or job) and hev to use a different programme, always put it on the airline to "stauts match" as they call it. (Yes, I've done this too.)
BUT, living in Oz, you should CALL the program manager locally and see what they do locally. Do they have a member golf day or other functions? "What's in it for me?"
Important for me is their technology. SQ's is second to none at this point. You can do everything you want online. Especially the ability to check-in, in any class, and choose or change your seat.
Their exclusive "Book the Cook" service is undervalued. In J & F you can actually choose your meal from an extensive list up to 24hrs prior to departure.
Overall, join the programm of the airline which you are likely to fly more. While yes, elite level alliance statuses are recognised across all members, you will always (yes ALWAYS) get a bigger smile at evey customer touch point from the airline whose programme you actually belong to.
EG, I know that CX will upgrade their own elite members before a oneworld member. At SIN Changi airport, there is a "Star Alliance Lounge" where all the non-SQ members have to go. Its a lounge, but inferior to SQ's own product. etc