Literary scholars maintain that Shakespeare's Antony and Cleopatra was written in 1606 or 1607 during the Renaissance era (1550-1660). On the other hand, Dryden's All For Love was written in the latter part of the 17th century (1677), which encompassed the neo-Classical period (1660-1798) in English history.
Basically, neo-Classical literature differed from Renaissance literature in terms of its approach to morality. While neo-Classical literature appeared to be dogmatic in character (inflexible or unyielding in its emphasis on certain moral principles), Renaissance literature emphasized experimentation and invention. The Renaissance era celebrated the idea of man as being inherently good and possessing of unlimited potential for spiritual and intellectual growth. Meanwhile, the neo-Classical era focused on the fallibility of man.
In his play, Dryden highlights the limitations of language to perfectly define its human referents. What this basically means is that it is difficult for language to keep up with fluctuating human nature and to describe it perfectly. In All For Love, Antony laments to Ventidius:
I know thy meaning.
But I have lost my reason, have disgraced
The name of soldier, with inglorious ease.
Essentially, Antony laments the inconsistent nature of his character: is he lover or warrior? If he is called by the name of "soldier," does it negate his right to be a lover as well? In Shakespeare's Antony and Cleopatra, Antony makes a similar lament to Eros in Act 4 Scene 14:
Here I am Antony,
Yet cannot hold this visible shape, my knave.
I made these wars for Egypt, and the Queen,
Whose heart I thought I had, for she had mine
However, there is a difference in language between the two interactions. In Antony and Cleopatra, Antony laments his schizophrenic double nature, but his musings are left unchallenged by Eros. Antony likens himself to ever-changing clouds, and Eros does not disagree. Here, Shakespeare explores the mutability (changeability) of human nature and the limiting ability of language to define this mutability. On the other hand, Antony's lament to Ventidius in All For Love is met with stirring exhortations to strengthen his failing resolve and to redeem his masculine honor:
No; 'tis you dream; you sleep away your hours
In desperate sloth, miscalled philosophy.
Up, up, for honour's sake; twelve legions wait you,
And long to call you chief: By painful journeys
I led them, patient both of heat and hunger,
Down form the Parthian marches to the Nile.
'Twill do you good to see their sunburnt faces,
Their scarred cheeks, and chopt hands: there's virtue in them.
Here, Dryden uses language to highlight the importance of preserving constancy and honor, the only means of man's salvation. This is the neo-Classical emphasis on dogmatic principle I mentioned earlier. Neo-Classicists believed that principle should over-ride emotion. Contrast this to the Shakespearean (Renaissance) idea of man as a figure in a constant state of flux and experimentation: this is the idea of man as ever-changing as the clouds in Antony and Cleopatra.
For more, please refer to the sources below.
1) Res et Verba: The Reform of Language in Dryden's All for Love by Robert L. King, ELH, Vol. 54, No. 1 (Spring, 1987), pp. 45-61
2) Language Fixation in Dryden's All For Love by Marcus Nordlund.
In his play, Dryden preserves the neo-Classical emphasis on the three unities: the unity of time, the unity of place, and the unity of action. Dryden's play is set predominantly in Alexandria, Egypt, while Shakespeare's play encompasses Greece, Egypt, and Italy. In terms of the unity of time, Dryden chooses to focus on the last stages of Antony's life.
Meanwhile, Shakespeare presents a more panoramic view of Antony's life in Antony and Cleopatra: he chooses to highlight the historical power struggle between Antony and Caesar, Caesar's betrayal of Lepidus, the death of Antony's first wife, Fulvia, and Caesar's defeat of Pompey. Here, you can briefly describe these events by referring to Shakespeare's play or eNotes' act by act summary of the play.
You may also be interested in one interesting plot difference between the two plays: Dryden's creative inclusion of the interaction between Octavia and Cleopatra. Use the text to describe this fascinating interaction between the two women, and highlight Dryden's reason for this creative licence:
I judged it both natural and probable, that Octavia, proud of her new-gained conquest, would search out Cleopatra to triumph over her; and that Cleopatra, thus attacked, was not of a spirit to shun the encounter: And it is not unlikely, that two exasperated rivals should use such satire as I have put into their mouths; for, after all, though the one were a Roman, and the other a queen, they were both women.
More to follow about the characterization of Cleopatra in both plays.