As well as building new vehicles, you can give them more armour and bigger engines. You can even upgrade your turrets, make harvesting more efficient, and research bigger and stronger walls. The weapons also work significantly differently on different vehicles. Autocannons are good for light mechanised infantry but don't do enough damage on the bigger tanks, for which you need ion guns or rocket launchers. It all works really rather well.
Explosions do look rather nice.
Unfortunately any strengths the game has are outweighed by its weaknesses, which become apparent all too soon. You'll come to realise when you create the first tank rush of the game that the engine simply can't handle the number of units you need to win it. Scrolling suffers first as it starts to jump and jerk all over, and then the units begin to move in a kind of time-warping fashion as they take sudden jumps halfway across the screen. Building lots of units also exposes the rather atrocious path finding. Select more than three or four units and they really will have trouble going in a straight line with no obstacles in-between themselves and their destination.