it's all a mith. I posted an article on the comparation of early morning vs. any-other-time-of-day cardio...
the lowdown is this: What REALLY matters is that you do it. At the end of the day, what matters are cals in vs. cals out. As long as you do your cardio, youwill burn those calories, depending on the intensity of the cardio, a numbers of cals will be from fat, others from glycogen.
Advocates of morning cardio say that since glycogen stores are low in the morning, your body will tap into fat faster... well, go figure.
I never did morning cardio before, I did allways after my lifting in the evenings, when my glycocen stores were already low, but after a whole day of eating.
This, together with the "low intensity cardio vs. HIIT", are the questions concerninc cardio that will never be answered to the deligth of 100% of the population.
my advice? do as your schedule allows it, but DO IT, damn it.