I think that QFFF can be better than some other OW schemes for earning status. So if you're going to earn more miles than you can use, and status is important, that might be a good reason to stick with QFFF.

In addition, some people may find the QF-specific status benefits useful.

And some people may have a good flow of non-flying miles to put into a QFFF account as well, when they couldn't be put into any other OW scheme. Being able to aggregate miles from more than one source may be useful for some people.

So as always, it depends on exactly how you use the FF scheme, and what your aims are. There's no one single answer.