the difference is in the minerals and other nutrients.
The darker the syrup (grade B at least)the more concentrated its 'food value' which is a real consideration on the MC. The purpose of the M.S. (or the blackstrap molasses: organic, unsulphered) is not to sweeten the drink -- it's to give your body everything it needs along with the lemon juice and water, to sustain itself, AND do the housecleaning as well. If the body were actually in 'starvation' mode, it would tend to hang on to all the toxins too, that the Master-Cleanse
is working at expelling.
If you can't get grade B, you might go with the molasses for a few days.
I personally always use it. It has the most minerals, iron, the B vitamins, etc...