Australia will win
India will win
NATO would likely help them as even though they are not full members there is a strong relationship.
Just because of their allies.
army and navy is just a little more up to date that could turn the tides for them
India may have many soldiers but they can't all swim to Australia. And even if they found a way to transport all of their soldiers here it is deemed impossible to invade Australia due to it's deserts and position. AUSTRALIA WINS
A population of over a billion. Would have more people to conscript.
The size of the Indian army and navy is bigger than the Australian ones, giving India the upper hand.
India too has allies like Russia and America.
Without allies, India has sheer numbers and manpower (and I really doubt Australia has a huge military budget, what threats do they have? New Zealand?)
It is obviously India. India possesses the worlds second largest population with this they could field an army of millions to defeat Australia. They also have the ability to use their millions of laborers to build a massive naval force capable of an invasion. India also has a superior submarine force which could pick off any Australian naval forces defending the coast, they could also be fielded for reconnaissance purposes. India and Australia have a similar strength in air forces, so the fight for the skies would be bloody quick and decisive, the only difference is India has the ability to produce planes on a larger and quicker scale. Australia also lacks a capable air defense in its western territory as they have focused on their Eastern shores for air defense. Another advantage is India will not have to stretch supply lines as far because they could use Sri Lanka as a forward operation base. Also even if Australia Manages manages to defeat the invasion fleet India can use its massive ballistic missle force to rain down on the Australian coast. This would destroy most defenses and another invasion force could be assembled, and once Indian forces make landfall and secure a beach head its over their superior numbers would sweep over the thin austailian lines and a break through would take place, once this happens Indian troops would sweep across the country side destroying the Aussies infrastructure causing the Australian war machine to collapse and lead to an ultimate surrender giving India their victory.