The "problem" with FF schemes is that any competitor can copy them. They no longer, if ever provide any real strategic advantage.
As for "loyalty" many people are members of 2,3 or more schemes anyway.
For business reasons a couple of years ago my employer asked me to research the empirical research on loyalty programs. The research shows that the schemes don't make the return that was first expected.
So I guess SIA only has to be similar, will depend on their award booking rate, fees, taxes etc.
Hint to SIA and Westpac: A nice "launch" bonus would be good.