Grade B maple syrup is only different from grade A maple syrup because it is harvested later in the season. Choosing between the two is just a matter of taste, and both are great in recipes and when making maple candy.
Whenever you buy pure maple syrup, you'll see a little seal that says what grade the maple syrup is. In terms of purity, there is no difference between grade B maple syrup and grade-A. Only PURE maple syrup is given grades—Log Cabin, Mrs. Butterworth, Aunt Jemima and others have to be called something like "pancake syrup".
One characteristic of grade B maple syrup is that it is darker in color. The general rule is that lighter maple syrup is harvested earlier in the season, and darker maple syrup later. That's just the result of nature, and maple sugar farmers have no control over how much of each maple syrup grade they get year-to-year.
Grade-b maple syrup also has a stronger flavor than grade-a. Many people use this at the breakfast table, but because a little bit goes a longer way, it's often used in smaller amounts for cooking.
All in all, grade B syrup is just as good as grade A. Grade A is not rarer than grade B, and they both taste great. What is important is that grade B is 100% pure maple syrup. That's all you need to include it in recipes or make delicious maple sugar candy.
