I would actually prefer to keep the 3 playoff teams per league with a bye for the league winner. I prefer smaller playoffs and feel like the road to climb from the bottom of a large division to a playoff contender should be harder to make in one season.
However, if we're going to have 4 playoff teams, then I prefer the two division format with the top two teams from each division making it. That keeps the rivalries within the division, and while it lets a potentially weaker 2nd place team into the postseason, I think the rivalry aspect is worth it.