One of the major differences between the two accounts of the beginning of life for humans and their subsequent fall from grace is the way in which in the Biblical account, very little mention is given at all to Satan in terms of the role that he plays. He is at best a flat character who is not fully developed. We know nothing of his background and are given no more information about him or for his motives for wanting Adam and Eve to eat the fruit.
However, in Paradise Lost, in many ways Satan is the principal character. Milton goes into great depth in terms of the way that he is characterised and described. We know his motives and we get a real flavour of the kind of individual that he is. Milton succeeds so well, in fact, that some critics argue Satan is a more realistic and likable character than God himself in this text. Consider the following quote as an example:
Here at least
we shall be free; the Almighty hath not built
Here for his envy, will not drive us hence:
Here we may reign secure, and in my choice
to reign is worth ambition though in Hell:
Better to reign in Hell, than serve in Heaven.
This famous quote seems to perfectly capture Satan's character and his resilience and resourcefulness when massive odds are stacked against him. This is the major difference between the two texts. Milton explores the face of evil much more deeply in his account, and we are left with the rather disturbing feeling that Satan is the more attractive character.