I haven't tried the new Baker's sugar, but I do have a comment about your
question.
This dilemma is exactly why I prefer recipes that offer ingredients in
weight rather than cups -- some cookbooks offer both, and the question you
pose could be the reason why sometimes the weight and cups don't match in
these recipes. When this happens, I usually go with whichever quantity is
less, since I don't like very sweet desserts. Over the years I started
reducing the sugar slightly in most recipes and found that it didn't make
any difference in the final product.
So you might try weighing a cup of the sugar you normally use, then
weighing a cup of the new sugar, and making a decision from there about the
quantity.
Pat