It's not so much the period as the personalities of the sculptors.
First Donatello sculpted two Davids. Then Verrocchio sculpted one. Then Michelangelo sculpted one. Which do you mean by 'the second'?
A quick wikipedia search is likely to tell you all you need to know about Michelangelo's David. Click link below! There are three more Davids in Florence: two by Donatello, one by Verrocchio.
There are different Davids. The one in the Bible, that was sculpted by Michelangelo, was a teenager.
Sometimes optical illusion distorts things. Michelangelo had to make the hands in different sizes so that they would look proportioned. The same happened with the Pieta sculpture, also by Michelangelo. The arm of Christ is much longer than an arm in real life (it would go bellow Christ's knees if he stood up) but it looks perfectly proportioned (because of optical illusion) when you look at the statue.
Fadlu Davids was born in 1981.
The ISBN of An Army of Davids is 1595550542.
Adolf Davids was born in 1867.
Faiek Davids was born in 1964.
Courtney Davids is 5' 10".
Edgar Davids is 169 cm.
Julia Davids was born in 1972.
Henry Davids was born in 1980.