Short answer: yes, there is always a difference in run time.
Long answer: run time depends on the capacity of the battery, and every battery is different, even when the physical size is the same. You have to look at and compare the specific batteries you plan to use.
The 64623 is 12 V 100 W so it will draw about 9 A (or more) when over driven.
Ordinary AA cells won't cut it, so you will need special cells.
It seems like high power AA cells come in at around 1500 mAh. High power 2/3A seem to come in around 1000 mAh. So you would probably get longer run time from suitable AA cells. Your total run time is only going to be about 5-6 minutes though, in few second bursts. It will be a fun light, not a useful light.
High power sub-C's do better at 3000 - 4000 mAh, but I don't think you can fit a large number of them into a small light.
Why 15.6 V? 12 x 1.2 V = 14.4 V, and 15 x 1.2 V = 18 V. I'm not sure how you would get 15.6 V with a round number of cells?
