But, I would really like to know if there is a 1-1.5 hour battery life difference. I know it doesn't really make too much technical sense.
As others have said, there really shouldn't be a difference. Just consider that most of the time your CPU is going to be throttling itself down to conserve battery life. At those times both the 2.3GHz and 2.6GHz models are likely running at a fraction of their full speed with the unused cores turned off.
Even running at full speed both chips should be pretty close.