First of all, the criteria for getting on the electoral list are not the same. People move around a lot. People are required to have lived at the same address for six months in order to be registered on the Quebec list. That is not true in the case of the federal list. The federal list includes all the residents, regardless of whether or not they have lived at their current address for six months or not. There are all sorts of factors of this type that come into play and that give rise to some variations, but I must say that Quebec probably has the most accurate voters' list.
On February 24th, 2009. See this statement in context.