I think both can help affordability, but to me, both are more demand-side measures.
The way to fix the housing supply problem in Canada and get people out of having to take these oversized mortgages they won't necessarily be able to afford in the future is to build more housing. The supply side is where it has to come from.
As my friend Ron talked about, in Toronto there are many condos sitting unsold, and the condo market is in a big downturn there. The demand is really for single-family homes and not condos, for the most part, at least. Giving the market time to fill that demand and having the government help them do that would be ideal.