I love Heroes 6, but it don´t reach near Kings Bounty.
Heroes 6 is too fast, you always search for new Towns or Unit Buildings. You can´t play slow and really tactical, because it is always the same. Taking all possible Buildings as soon as possible and you win, the KI is not really good.
Kings Bounty instead had no timeline. All neutral monsters had the same strengh from the beginning. And you don´t get greater armies at only sitting in the castle and wait a few turns. Thats a really bad thing that is in my opinion the biggest problem in all Heroes games.
The KI instead always attacks with weak armies and at the end there are not really big battles, because the KI had lost too many units at the weak attacks. No compare to Heroes 3.
The castle Building is also not really good at heroes 6, there are no really choices what to build. The same are the skills, there are a lot more in compare to kings Bounty, but there are not many that are good, the most are useless or too weak.
Heroes 6 had no really good spells, the most are the same thing only stronger with other names, not really spells to think and then play with.
The Boss battles in Heroes 6 are a joke and the races are not really different, the units are not better, the unit design in Kings Bounty (Stats, Different, Skills) is 1000 % better.
But i play Heroes 6 - it is a really good game, but if tomorrow comes a new Kings Bounty i would never play Heroes 6 before i played the new Kings Bounty 6 times from beginning to the end.
Heroes 6 make many things better than the previous Heroes games, but Kings bounty is the King of all turn based strategie.