Well, all eight statues are very similar. Like I said I haven't studies too much past the Baroque, outside of the US at least. If I had to take a guess, I would say that the style the latter four are at the very least an attempt to mimic baroque art. The best way I can explain why I think that is to explain the progression from early rennaissance to baroque. And I have just the statues to illustrate it for you. It is all about the moment.
This is Donatello's David and it was created around 1440.
And this is Verrochio's David which was created around 1475.
Both of these are relatively early rennaissance so they are pretty similar. Notice how both pieces show David after slaying Goliath. The figures are calm and relaxed. The viewer is meant to see the moment in time when David is reflecting on his victory, maybe dwelling on God's divine help, or perhaps he is meant to be thinking of his own greatness. Perhaps in Donatello's piece he is more focused on God, as he seems a little more humbled, with his head down. And Verrochio's piece is meant to show the confidence and self assuredness of a youth. (Notice on both pieces the head of Goliath at their feet.)
This is Michelangelo's David, it was unveiled in 1504.(Probably the most famous one.)
In this piece we see something different. This is the figure of David prior to slaying Goliath. Michelangelo has focused on the moment when David sees Goliath approaching. Notice the emotion that Michelangelo has expressed in David's face.
This piece has taken the concentration from the idea or moment of triumph, to the idea of the human will to triumph. He seems relaxed, but his exagerated muscular features (look at the hands and arms in particular) make him seem tensed, like they are prepared for what is about to happen.
So, so far we have seen the moment after victory, and the moment prior to victory, which leads to the last example which is from the Baroque period and is my personal favorite.
This is Bernini's David. 1624.
Bernini has shown David right in the act of slaying Goliath. This is the most extreme case of a contrapposto stance that we have seen in a figure of David. His body is twisted while his arms are frozen in time at the point where he has just begun to hurl the rock. Notice the expression on his face. He is not thinking about what he has done, or what he has to do. He is doing it. While the figure is still, Bernini has masterfully crafted this piece to exude energy.
Anyways, you can surely see this idea in your Baroque examples, as well as your more contemporary ones. Dynamic compositions, full of the action, and do not forget emotion, of the moment of battle.
I'm sure there is a way to tell exactly how they are different, but seeing as how I haven't studied the era that the latter four were made, I would not no how to contrast them.