Quebec minor hockey has fallen off in the last 20 years or so, which is why you don't see as many Francophone players in the NHL these days. The costs and economics of the region play a big role, and hockey is starting to lose some ground in terms of popularity from its once impenetrably dominant position. Of course an individual team in the Q can still be pretty stacked and compete with the best of them in a given season, especially considering how teams will load up in a given year (if they host the Memorial Cup or otherwise). The QMJHL also has the smallest number of teams (not a major difference but certainly helps at the margins). There is also a confounding factor where a lot of kids in the WHL's region will opt to play Junior A and preserve their NCAA eligibility as well, because the WHL has a very tough travel schedule and covers a wide geographic region, so it's not ideal for all players. The QMJHL is also the most reliant of the three leagues on helping to build up their rosters through the Import Draft, in part also because the only American states covered in the QMJHL's territory are New England, and there are good hockey playing opportunities out of U.S. Prep Schools for players there.
Overall though, I would say the QMJHL is the easiest of the three Major Junior Leagues to make, and the OHL is the toughest. A lot of kids getting regular shifts at the QMJHL probably wouldn't make the rosters for any OHL team.