What is the difference between the “Tribes of the East” and the “Hammers of Fate” expansions?

Hello, today I saw two discs in the store, one is called Heroes of Might & Magic V: Tribes of the East, and the other is Heroes of Might and Magic 5: Lords of the Horde, priced at 200 and 300 rubles respectively. I searched the internet, but I still don't understand the difference between them.
I've played the regular Heroes of Might & Magic V and Heroes of Might & Magic V: Hammers of Fate, so that's clear.
Which disc should I buy to continue the game? And what's on the other one?