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 Defence 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.
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.
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"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.
"Right now Japan is in better shape," he told AFP.
Even Chinese President Xi Jinping has urged the military -- which is beset by corruption, with high-ranking officers under investigation -- to improve its abilities to "win battles".
China's first aircraft carrier, the Liaoning, went into service 18 months ago and according to the International Institute for Strategic Studies' Military Balance 2014 report, published in February, the country's forces outnumber Japan in virtually all areas.
China's defence budget was USD 112.2 billion last year, while Japan's came to USD 51 billion, according to the report.
"The PLA is engaged in a modernisation programme fuelled by the country's rapid economic development that has seen it surpass the armed forces of less developed countries in Asia," the report said.