I liked the first game, and the expansions.
Although, there you generally found a phalanx unit combo and went around in a mob killing the enemy. - Oh, in single player, didn't do much multi in that one.
In DOW2, in the campaign, you control no more than 4 units at a time, and at the point I'm at in the campaign I have 6 units to choose from.
So its much smaller squadbased, with a teamleader who is a powerhouse, and 2 or 3 marines in their squads.
The setting has several missions at any given time, and you have to perform admirably to be rewarded with more attacks in the same day... And you need those or the tyranids infest the planets, so there is a "timer" of sorts that really heightens the tension on a strategic level.
Well, I'm going back in...