Local is the biggest impact, to my understanding Xbox doesn't have much of a market share outside the English speaking world, Playstation does. Xbox 360 was a bit ahead of the PS3 in the US/Australia/UK, but not in Asia and congenital Europe.
I seem to recall reading that the XBox doesn't sell well in Japan due to it's name: X (battsu) being bad, wrong, or "no". It's why in Japanese PlayStation games circle is confirm and x is cancel.
