Fighter A is a professional heavyweight boxer.
Fighter B is a jujitsu wrestler.
Fighter C is a karate man.
In fight 1, It's karate vs. boxing. The boxer is agile and fit, but when he closes the distance, the karate man snaps a kick to his groin. The boxer, unfamiliar with the low kick and unable to block it, drops his hands in agony. The karate man is able to kick him in the head and run away. Winner= Karateka.
In fight 3, The wrestler faces the boxer. The wrestler shoots for a double leg take down, but the boxer is able to stick jabs in his face every time. Unable to take the boxer down, the wrestler is punched repeatedly until knocked out.
Each fighter beat another, and was beaten in turn. Was it some flaw in "style"? No. Each man proved he could make his style work. The trouble is, in a personal defense situation, what matters is what will work for you against this attacker. If his goal is to punch you to death, maybe trading punches is not a great idea. If he tries to pin you to the ground, maybe that's not where you want to be. Personal Defense requires being flexible and responsive to the situation. That is a skill that only individuals can acquire - a style can't do it. As always, it's all about YOU!