I don't think it's quite correct to say Azo has higher Dmax or anything like that.
The absolute value of Dmax is mostly limited by the paper surface. Glossy surface is the best in terms of Dmax, but in reality not everyone likes glossy, especially in RC.
The Dmax is not very useful measure of the deepness of the black, unless you are making the print all black. Instead, the shape of the shoulder is important. Paper with a rather abrupt transition from straight line to Dmax tends to give most crisp shadow. One reason for this is obvious, because of increased shadow contrast. But reduced exposure required to reach Dmax in abrupt shoulder emulsion is also helpful in reducing the flare in the other parts of the image.
But that is mostly of some academic interest. In real pictorial image, you rarely need to use the entire desntiy scale of the paper, and it's unnecessary to worry about reaching or utilizing the Dmax.