re: Better Super Bowl career: 4-0 or 3-3?

The difference is the parity in the NFL now due to free agency. The Cowboys of the 1990s were the last dynasty team that stayed intact for 5+ years. Belichick had to trade off the core of his teams from the early 2000s (Seymour, Ty Law, Milloy, etc) and still maintained his success. The three that have made it to SBs since his last title have all been 90% new teams.