Just buy Medieval 2 if you want tactical combat
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In Dom tactical combat wouldn't fit too well imho, the current system is working well enough. Imagine all the MM you would have to do if you could control everything. I think Illwinter would have to make a completely new Dominions for that from scratch. I doubt that this redone new Dominions would be more enjoyable than than the current Dominions though because they would have to use an approach like CA for TW i think, otherwise it would be a MM nightmare.
Medieval 2 is great, but it cannot be compared to Dominions. Dominions is also great, but those games are two different subgenres, so they cannot be compared at all.
So just decide to your liking, or if you have no strong preference enjoy both games.
I am currently in gamers heaven with MTW 2 and Dom 3
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