The two main characters both have idol's they look up to for inspiration to become as great if not better wants their fighting careers have reached the world level. Both protagonists have a very troubled past that leads them into becoming a fighter to protect the people close to them. Both manga's have a substantial understanding of mix martial arts with in depth techniques and strategies that make for very interesting fights.
Both are just pure fighting series and I would even say Koukou Tekken-den Tough is even more amazing because it seems relatively realistic, at least more than Baki. So if you like all out martial arts series like Baki or Koukou Tekken-den Tough, check out the other one!