We are offered to play a match.

The difference in rules is observed as follows:
1. Restarts. On H6 there is no restart for a 1-1-6 matchup, on HW there is.
2. Heroes. There are differences regarding the use of spells obtained from level 4 specialty heroes. There's no point in detailing them; look carefully yourselves. But pay attention: On H6, Tunt is restricted, as are level 4 specialists, on HW it is not.
3. Scrolls. On HW, the requirements for magic building, which grants the right to use scrolls, are more flexible, but there is no 6th week rule. On H6, there is.
4. Necropolis. On H6, the starting hero is random, goodbye Gosha.
5. Diplomacy. On H6, it is completely banned; on HW, it is limitedly allowed.
I have only given an overview, not a detailed analysis; to be certain, look and analyze it yourselves!!!