Last generation the XBox was noticeably more powerful than the PS2 and had the added advantage of being easier to develop for too. In this generation it is plausable that the PS3 is more powerful than the XBox 360, but when you factor in the difficulty developing for the PS3 the difference between the PS3 and XBox 360 is (far) smaller than the difference between the XBox and PS2.
At the same time, the ammount of additional processing power you need to get noticeable (and worthwhile) improvements in games today is far greater than the ammount of additional processing power you needed to get noticeable (and worthwhile) improvements in games in the last generation.
When you combine these two factors the difference in processing power between the PS3 and XBox 360 is not large enough to justify the countless arguments that take place on this (and every) forum every day.
