The two Asian powers are embroiled in simmering territorial and historical rows, with the tensions highlighted this week in consecutive visits to each by US Defense Secretary Chuck Hagel.
Beijing's latest double-digit rise in its defence budget, announced last month, will only increase its numerical superiority, but Japan enjoys technological and training advantages, and the key asset of a US security umbrella.
Hagel reiterated Washington's support for Tokyo while criticising Beijing in blunt exchanges with top People's Liberation Army (PLA) generals.
China, for its part, told the Vietnam War veteran that sovereignty over islands in the East China Sea at the heart of the dispute with Japan was non-negotiable and that it would "make no compromise".
Despite such tough talk, analysts say China's top strategists know an armed conflict, intentional or accidental, is not in their interest and could detract from their long-term goal of expanding their regional and global power.
"The Chinese high command has got to be very prudent and cautious in terms of the launch of any kind of military operation," said Arthur Ding, an expert on the PLA at Taiwan's National Chengchi University.
Even without the benefit of the US security alliance, Japan currently has better training, facilities and equipment, Ding said, although the long term situation was less clear.
"Right now Japan is in better shape," he told AFP.
