<p>Michaelangelo's is the first to show impending action. It shows a David ready to face Goliath and is visually more intense than Donatello's. It seems more classically rendered, though one notices that the proportions are a bit off (head, hands are too big) - Michaelangelo's idea was that it was up to the artist on how to depict things.</p>
<p>But you've probably already mentioned that. I guess you could write about the original commissions and where the pieces ended up. Michaelangelo's was meant to be in a church, but the Florentines loved it so much (they saw their city as a David fighting among Goliaths - hero vs. his enemies), they put it in the center of town. I don't know about Donatello's, though, but that could get you a decent paragraph.</p>