Gillard, an unmarried female prime minister with no children, a hairdresser boyfriend and no religious commitment offers a radical alternative to the devout Catholic family man Abbott.
Voters may look at a choice between the God-fearing, rugby-playing, boxing, surf lifesaving triathlete and married father of three, and a career-minded woman who is clearly tough and effective.
Abbott - the "Mad Monk" of Australian politics who cheerfully once described himself as a "junkyard dog attacking the other side" - or Gillard, a skilful operator who has navigated the treacherous currents of Australian Labor Party politics.
Both have the gift shared by the best Australian politicians to skewer rivals with withering insults. Abbott once said Gillard had a "shit-eating grin".
The new Prime Minister is no slouch herself. During the last election campaign, she called John Howard a "political parody of pantomime" and once labelled Abbott a "snivelling grub". She is said to have the mind of a lawyer and the mouth of a bricklayer.
Fitness-freak Abbott is an obsessive cyclist and gym-nut. At Oxford University he took up boxing. In his first bout, against Cambridge University, he knocked out his opponent within the first minute. He made similarly short work of challengers in three other fights, employing an all-out attack he proudly called "the whirling dervisher".
Writing in the Melbourne Age newspaper, Annabel Crabb saw plenty to admire in Gillard's toolkit while she was still number two: "There really isn't any doubt any more about whether the deputy prime minister, Julia Gillard, has the killer instinct. The problem tends more to be how to drag her off the victim's body."
She is clearly comfortable wielding power and the more power she gets, the better she appears to perform.
On each other
Gillard: "I think I'm a much more normal person than Tony Abbott."
Abbott: "On those rare occasions when she lets her hair down she can be a charming companion. And I've certainly enjoyed her company a couple of times in a social context, and I think it would be good to see more of that side of Julia."
Abbott's mother said her son - who at the age of 26 entered a Manly seminary but left before taking his vows - would either become Prime Minister or Pope. At university Abbott rescued a boy from drowning and once helped people from a burning house. He did not brag about his heroics. For many years Abbott wrestled with his conscience after a university girlfriend fell pregnant and adopted out the baby. When he found he was not the father, he was gracious toward the woman who had wrongly identified him as such.
In Gillard's first year as deputy, outspoken Liberal Senator Bill Heffernan said the Labor MP was unfit for leadership because she was "deliberately barren". Senator Heffernan was derided at the time, but Gillard accepted his apology. She later remarked: "I'm kind of full of admiration for women who can mix it together, working and having kids, but I'm not sure I could have."
Abbott must balance his instincts with his clear-eyed conservatism. His easy-going banter and ability to connect with the electorate are big assets. His Achilles' heel may be his impetuosity. Gillard, having endured taunts about her Nasal voice, hairstyle, dress sense and failure to embrace domestic life, must convince an electorate that it can trust a leader installed over the carcass of her predecessor, and win back voters who have become disenchanted with her party.