2 of last 3 and 4 of last 6 super bowls have been won by teams with 4-3 defenses. The only true 3-4 winner was steelers, because packers showed a lot of other looks out of their base 3-4. It's an even split over the last 10 super bowls with 5 wins each (bucs, colts, giants 2x and saints), 3 - 4 (2 apiece steelers and pats, pack 1)
When you look at really matters, rings and how does the D hold up in post season, the notion of 3 - 4 superiority is quickly dismissed.