The O has always had the most elite offensive talent, the defense & goaltending can be non existent at times. Almost always recognized as the best of the 3 CHL leagues.
The Dub has historically been the most defensive, most physical, tighter structured, better goaltending league, but this is changing with the elite talent level increasing in Western Canada. The Dub is still a bit behind the O but it has closed the talent gap significantly.
The Q has always been known for the no defense high scoring style, and in recent years, the talent level has dropped off a cliff, as Quebec is the poorest province so many people can't put their kids in minor hockey as hockey & everything else has gotten more expensive. Even more haves and have nots in terms of individuals and teams in the Q. And before the rule change, you were seeing more and more Q territory guys bypassing the Q and going south to the NCAA, weakening the league further.