You can choose how you wish to co-operate with PowerGrades, as everything is under your supervision. You can see exactly what is being performed in each node, and you can make adjustments as needed. You can turn every node off and on, alter the intensity of each one, and change any value of every node as you see fit.
With a LUT, all the attributes are created into a solitary curve. You can modify the intensity of a LUT, and there are a number of strategies on how to deconstruct a LUT to a point. But never completely. A LUT may have math inside which can create their own look, which cannot be achieved with a PowerGrade. A LUT is not better or worse than a PowerGrade. It’s just another option.