I think a national strategy is preferable because it focuses the energy.
Quebec is a unique case in that it was the first jurisdiction to implement a comprehensive anti-poverty strategy, and it's been going for several years now. It produces an annual report. It's doing very well. Unfortunately, there's only one other province doing the same kind of thing, and that's Newfoundland and Labrador. So the fact that Quebec is doing so well doesn't mean that everybody else would too.
Plus, there are programs within federal jurisdiction, such as the ones I mentioned--the pension system and the EI system--although Quebec is the exception there, too, in that it has its own maternity benefits program through EI.
Altogether, there are things the federal government could do, but it needs to be comprehensive and done in conjunction with the provinces and probably also with the municipalities.