What about considering a combination of all three?
Macbeth himself possesses an ambition and an impatience which, if given sufficient rein, will be the instruments of his downfall. The witches provide the prophecy which, when the first part is fulfilled and he becomes Thane of Cawdor, causes him to consider, briefly, murdering Duncan. He debates the idea, at this point a fallible but essentially moral man who is disgusted by the 'horrid image' of murder (and remember this is not just any murder, but regicide) and decides that 'if chance will have me king...chance may crown me' without his having to intervene. When he learns that Duncan plans to make his eldest son Malcolm his successor, he becomes tempted to pre-emt fate again, but still he is aware that these thoughts are evil.
It is of course his Lady who actually prompts the murder, and is shown to have far fewer moral scruples than her husband. Undoubtedly it is she who influences him most at this point in the play, because she plays on all his weaknesses, accusing him of not being 'man' enough to kill the king.
Once the king is dead, his guards framed for his murder, and Duncan's sons gone into hiding, Macbeth is named king. But now, the Witches' prophesy becgins to haunt him again - now he must deal with Banquo, whose heirs are to be king. When he sees the Weird Sisters again, they warn him about Macduff.
From here on, Macbeth's tyranny has escalated, and he himself organises the assassinations of those who stand in his way (both botched to an extent - Fleance escapes, and Macduff's wife and children are killed, but Macduff is absent and thus survives.)
I suggest that 'influence' is a fluid thing as this complex play develops. Good luck!