The difference between beet sugar and cane sugar
White beet sugar and white cane sugar are virtually identical in composition, but there may be very small differences (~0.05%) which some cooks find affects caramelization. Reportedly, cane sugar will caramelize better than beet sugar in many cases.

The bigger difference is when you look at brown sugars. In beet sugar, molasses is added after refining to make the brown sugar, as the molasses that comes from beet sugar is not fit for human consumption. Cane sugar is simply a less-refined product where the molasses has been left in the product. So when baking with beet brown sugar, often the molasses hasn't fully penetrated the sugar granules and "rubs off".