DSP’s are mainly based on Harvard architecture to perform task faster with hard wired instructions as compared to Microcontrollers which are mainly available with von neumann architecture (some microcontrollers like PIC is an exception).
The DSP can compute the complex mathematical calculation of your application faster than the microcontroller can. Because that’s what it’s designed to do.
DSP have MAC(Multiply and accumulate) capability in a single cycle.
DSP have right sort of peripheral to integrate with high speed audio and Video codec